71828 that can be characterized in many ways. NHS 111, a medical helpline in England and Scotland. 3 2020–present: Further product launches, expansion to more markets, Carl Pei's resignation Such a number is algebraic and can be expressed as the sum of a rational number and the square root of a rational number. 1623), and ⁠ 142 / 45 ⁠ (3rd century, approximately 3. In number theory, a perfect number is a positive integer that is equal to the sum of its positive proper divisors, that is, divisors excluding the number itself. ; It is twice the third power of three, 3 3 + 3 3 = 54, and hence is a Leyland number. 8 is the only composite number with a prime aliquot sum of 7 (1 + 2 + 4) that is part of the aliquot sequence (8, 7, 1, 0). 1 1 Debby Boone 10 2 The Emotions 5 3 Stevie Wonder 4 Andy Gibb 5 Barbra Streisand 3 6 Mary MacGregor 2 Daryl Hall and John Oates Eagles Leo Sayer Meco Bee Gees 12 Rod Stewart 1 Marilyn McCoo Billy Davis Jr. The symbol has historically been used for a wide range of purposes including the designation of an ordinal number and as a ligatured abbreviation for pounds avoirdupois – having been derived from the now-rare ℔ . 1416. Constructible numbers form a subfield of the field of algebraic numbers, and include the quadratic surds. This includes the structure of words, phrases, clauses, sentences, and whole texts. 1556). ISSN encoded in an EAN-13 barcode with sequence variant 0 and issue number 05 Example of an ISSN, 2049-3630, encoded in an EAN-13 bar code, with explanation ISSN expanded with sequence variant 0 to a GTIN-13 and encoded in an EAN-13 barcode with an EAN-2 add-on designating issue number 13 1. 54 is an abundant number and a semiperfect number, like all other multiples of 6. 1) then a (i. The year 1 AD was a common year starting on Saturday in the Julian calendar. The number googolplexplex, is a 1 with a googolplex number of zeros behind it. Other texts show that numbers from 1 to 9 were occasionally supplemented by a placeholder known as sipos, represented as a circle or wheel, reminiscent of the eventual symbol for zero. In scientific notation, it is written as 10 8. Two is the only even prime number. 0 nor 1. 1–35), therefore the weight b 1 is 35 instead of 36. It is the third Mersenne prime of the form 2 n − 1, and the eighth Mersenne prime exponent, in-turn yielding the maximum positive value for a 32-bit signed binary integer in computing: 2,147,483,647. One Direction, often shortened to 1D, are an English-Irish pop boy band formed in London in 2010. It is the limit of (+ /) as n tends to infinity, an expression that arises in the computation of compound interest. The number of people affected globally is unknown, although it is estimated that about 80,000 children develop the disease each year. That year, 10 acts earned their first number one song: Gloria Gaynor, Amii Stewart, Blondie, Peaches & Herb, Anita Ward, The Knack, Robert John, M, Styx, and Rupert Holmes; only Blondie would ever have another number one hit. It works in every country of the EU, for land lines and mobile phones. A personal identification number (PIN), PIN code, or sometimes redundantly a PIN number, is a numeric (sometimes alpha-numeric) passcode used in the process of authenticating a user accessing a system. 5 million. e. Worldwide distribution of country calling codes. Users can switch carriers while keeping number and prefix (so prefixes are not tightly coupled to a specific carrier). In the context of the thermal fluids, the thermal Péclet number is equivalent to the product of the Reynolds number and the Prandtl number (Re × Pr). The first two are "primitive", and 65 is the lowest number to be the largest side of more than one such triple. It is also used in some other countries as an emergency telephone number for both mobile and fixed-line telephones. 7 are in the United States alone. The number e is a mathematical constant approximately equal to 2. The next perfect number is 28, since 1 + 2 + 4 + 7 + 14 = 28. It is defined as the number of constituent particles (usually molecules, atoms, or ions) per mole and used as a normalization factor in the amount of substance in a sample. In symbols, this is "10 × 10 = 100". These are also the two odd prime numbers that lie amongst the only all-Harshad numbers (1, 2, 4, and 6) that are also the first four highly composite numbers, with the only number that is both a prime number and a "highly composite number". The series had aired on Fox and currently airs on ABC . It was the first year of the 1st century and 1st millennium. For instance, 6 has proper divisors 1, 2 and 3, and 1 + 2 + 3 = 6, so 6 is a perfect number. 1 specified a design for any connector smaller than the standard type A or type B. 25 × 10 11) galaxies GS1 also acts as the secretariat for ISO's Automatic identification and data capture techniques technical committee (ISO/IEC JTC 1/SC 31). Letter frequency analysis dates back to the Arab mathematician Al-Kindi (c. (The old-fashioned term "evenly divisible" is now almost always shortened to "divisible". 0) marks the end of the number (it has just one digit), so in numbers of more than one digit, first-digit range is only b–9 (i. Moreover, a prime number is never palindromic in base if . 65 = 1 5 + 2 4 + 3 3 + 4 2 + 5 1. If there is only 32. Prior to 1969 there was no official singles chart; however, The Official Charts Company and Guinness' British Hit Singles & Albums regard the canonical sources as New Musical Express before 10 March 1960 and Record Retailer from then until 15 February 1969 when Retailer and the BBC jointly commissioned the British Market VIN on a Chinese moped VIN on a 1996 Porsche 993 GT2 VIN visible in the windshield VIN recorded on a Chinese vehicle licence. The emergency telephone number in New Zealand; see 111 (emergency telephone number). The number of ratified Amendments to the United States Constitution. 41; 1. It is the lowest positive integer requiring seven syllables to name in English (British and Commonwealth), or six syllables (by dropping the "and") in American English. The normal length of an EAN is 13 digits. A natural number can be used to express the size of a finite set; more precisely, a cardinal number is a measure for the size of a set, which is even suitable for infinite sets. For example, if the threshold value for the first digit is b (i. Introduced in 1958, the Hot 100 is the pre-eminent singles chart in the United States, currently monitoring the most popular singles in terms of popular radio play, single purchases and online streaming. For example, 5i is an imaginary number, and its square is −25. 1 ( one, unit, unity) is a number representing a single or the only entity. This article describes a generalized, present-day Standard English – a form of speech and writing used in public discourse, including broadcasting, education, entertainment, government, and news, over a range of registers, from formal to The set ω 1 is itself an ordinal number larger than all countable ones, so it is an uncountable set. The Doors scored their first #1 hit with "Light My Fire" in 1967. A Kaprekar number is a sociable Kaprekar number with =, and a amicable Kaprekar number is a sociable Kaprekar number with =. A natural number can be gotten by multiplying two numbers. Any natural number is equal to 1 times the number itself, so those two numbers are two of its divisors. The number of iterations i {\displaystyle i} needed for F p , b i ( n ) {\displaystyle F_{p,b}^{i}(n)} to reach a fixed point is the Kaprekar function's persistence of n {\displaystyle n} , and undefined if it never Simple English; Slovenčina McDonald's is the world's second-largest private employer with 1. In most English-speaking countries, it can be written with or without a comma or sometimes a period separating the thousands digit: 1,000. A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i. . The group is composed of Niall Horan, Liam Payne, Harry Styles, Louis Tomlinson, and, until 2015, Zayn Malik. Number 1, a slang term for urination; No. The EAN-8 consists of: Country-specific part: 2-3 digits; Article number: 4-5 digits; Checksum digit The UK Singles Chart is the official record chart in the United Kingdom. An imaginary number is the product of a real number and the imaginary unit i, which is defined by its property i 2 = −1. ) Any odd number n may be constructed by the formula n = 2k + 1, for a suitable integer k. 1 2013–2014: Founding and OnePlus One 1. Alternate, but less common, approaches include phonology (the spoken language) and the number of phonemes (sounds). The lower infectivity An electron state has spin number s = ⁠ 1 / 2 ⁠, consequently m s will be + ⁠ 1 / 2 ⁠ ("spin up") or - ⁠ 1 / 2 ⁠ "spin down" states. The lottery return percentage is 41. 1983–1989; ATP ranking's average system with bonus points for beating top ranked players. It is a superprime and a self prime (after 3, 5, and 7), as no integer added up to its base 10 digits results in 31. The year started on a Monday in the Gregorian calendar. Here are the Billboard Hot 100 number-one hits of 1979. It was adapted from French usage, and is similar to the system that was documented or invented by Chuquet . [2] In the unary system, the number 0 (zero) is represented by the empty string , that is, the absence of a symbol. 1 is also a numerical digit and represents a single unit of counting or measurement. 022 140 76 × 10 23 mol −1 (reciprocal moles). 1990–1999; ‘Best of 14’ ranking system, where a player’s best 14 results in the events counted. 1, an American rifle Few USB devices made it to the market until USB 1. For example 0+1=1 and 3+5=8. Within the United States the number of people affected is estimated at one to three million. For example: simplex, duplex (communication in only 1 direction at a time, in 2 directions simultaneously) 5,354,228,880 = superior highly composite number, smallest number divisible by the numbers from 1 to 24 5,391,411,025 = smallest odd abundant number not divisible by 3 [51] 5,469,566,585 = number of trees with 29 unlabeled nodes [52] The set of rational numbers is not complete. The golden ratio is also an algebraic number and even an algebraic integer. 5 is a square pyramidal number: 1, 5, 14, 30, 55, The first four members add to 50 while the fifth indexed member in the sequence is 55. The Péclet number is defined as: Several early Hebrew leaders and kings are said to have ruled for "forty years", that is, a generation. mass number (symbol: A), which is the sum of the number of protons and number of neutrons in the nucleus of an atom relative atomic mass (also called atomic weight ; symbol: A r ), which is the ratio of the average mass per atom of an element from a given sample to 1/12 the mass of a carbon-12 atom. q) where q is a higher prime. Prime numbers: If a number is not 1, and not a composite number, then it is a prime number. The telephone number 1-1-2 (or 112) is the standard European Union (EU) emergency telephone number. Two types of HIV have been characterized: HIV-1 and HIV-2. Therefore, ℵ 1 is distinct from ℵ 0. The definition of ℵ 1 implies (in ZF, Zermelo–Fraenkel set theory without the axiom of choice) that no cardinal number is between ℵ 0 and ℵ 1. The Monkees hit #1 twice in 1967 with "I'm a Believer" and "Daydream Believer". East Asian languages treat 100,000,000 as a counting unit, significant as the square of a myriad, also a counting unit. 8 × 10 26 metres), and contains about 5 × 10 22 stars, organized into around 125 billion (1. There is also a shorter version called EAN-8, for small packages, where the full 13-digit number would take too much space on the package. HIV-1 is the virus that was initially discovered and termed both lymphadenopathy associated virus (LAV) and human T-lymphotropic virus 3 (HTLV-III). On 1 March 2014, The Economist, in an article titled "The Future of Wikipedia", cited a trend analysis concerning data published by the Wikimedia Foundation stating that "[t]he number of editors for the English-language version has fallen by a third in seven years. 1-1-2. 1-Butanol, also known as butan-1-ol or n-butanol, is a primary alcohol with the chemical formula C 4 H 9 OH and a linear structure. For example, ten tens is the same as ten times ten, or one hundred. USB 1. Letter frequency is the number of times letters of the alphabet appear on average in written language. 65 is the length of the hypotenuse of 4 different Pythagorean triangles, the lowest number to have more than 2: 65 2 = 16 2 + 63 2 = 33 2 + 56 2 = 39 2 + 52 2 = 25 2 + 60 2. The name centillion was devised in the 19th century for the 100th "illion", being 10 303 in short form and 10 600 in long form, and is much bigger than a googol. The first prime (non-composite) natural numbers are 2, 3, 5, 7, 11, 13, 17 and so on. There are 5 vowel letters and 19 consonant letters—as well as Y and W, which may function as either type. Other large numbers, as regards length and time, are found in astronomy and cosmology. The first league event to feature this was the 1993 Football League Cup Final between Arsenal and Sheffield Wednesday, and it became standard in the FA Premier League the following season, along with names printed above the numbers. Following the codification of professional football by the Football Association in 1885, [1] the Football League was established in 1888, after meetings initiated by Aston Villa 1,000,000 (one million), or one thousand thousand, is the natural number following 999,999 and preceding 1,000,001. Rose Royce Manfred Mann's Earth Band ABBA David Soul A typical British bank statement header (from a fictitious bank), showing the location of the account's IBAN. For example, a line segment of unit length is a line segment of length 1. In English and many other languages, they are used to coin numerous series of words. Simple English; Slovenčina where the standard state concentration c 0 = 1 mol/L. The Arabic term for zero is sifr (صفر), transliterated into Latin as cifra, which became the English word cipher. Until 1835, the English Alphabet consisted of 27 letters: after "Z" the 27th letter of the alphabet was Ampersand (&) Because a dalton, a unit commonly used to measure atomic mass, is exactly 1/12 of the mass of a carbon-12 atom, this definition of the mole entailed that the mass of one mole of a compound or element in grams was numerically equal to the average mass of one molecule or atom of the substance in daltons, and that the number of daltons in a gram English has special names for some of the numbers in the decimal number system that are "powers of ten". HIV-1 is more virulent and more infective than HIV-2, and is the cause of the majority of HIV infections globally. The first number of the pattern is 0, the second number is 1, and each number after that is equal to adding the two numbers right before it together. Country calling codes, country dial-in codes, international subscriber dialing (ISD) codes, or most commonly, telephone country codes are telephone number prefixes for reaching telephone subscribers in foreign countries or areas via international telecommunication networks. The word Mach is always capitalized since it derives from a proper name, and since the Mach number is a dimensionless quantity rather than a unit of measure, the number comes after the word Mach; the second Mach number is Mach 2 instead of 2 Mach English grammar is the set of structural rules of the English language. 31 is the 11th prime number. There is an infinite number of prime numbers. 1547 (around 1 AD), (100 AD, approximately 3. 9-1-1 is an American procedural drama television series created by Ryan Murphy, Brad Falchuk, and Tim Minear. She was the last monarch of the House of Tudor. This ratio is a pure number whose logarithm can be defined. Since electron are fermions they obey the Pauli exclusion principle : each electron state must have different quantum numbers. 8 billion years (4. The number zero is considered to be both real and imaginary. Examples include Eli (1 Samuel 4:18), Saul (Acts 13:21), David (2 Samuel 5:4), and Solomon (1 Kings 11:42). Wikipedia® is a This is a list of songs that have peaked at number one on the Billboard Hot 100 and the magazine's national singles charts that preceded it. The golden ratio's negative −φ and reciprocal φ −1 are the two roots of the quadratic polynomial x 2 + x − 1. ∅ {\displaystyle \emptyset } The number in the Glenn Miller Orchestra's hit song "Pennsylvania 6-5000" (1940) is the number of the Hotel Pennsylvania in New York City. List of number-one artists by total weeks at number one Position Artist Weeks at No. These are the Billboard magazine Hot 100 number one hits of 1967. The International Bank Account Number (IBAN) is an internationally agreed upon system of identifying bank accounts across national borders to facilitate the communication and processing of cross border transactions with a reduced risk of transcription errors. Around 265 AD, the Wei Kingdom mathematician Liu Hui created a polygon-based iterative algorithm and used it with a 3,072-sided polygon to obtain a value of π of 3. (Mt 1,1-17) The number of Grievances of the United States Declaration of Independence. The unary numeral system is the simplest numeral system to represent natural numbers: to represent a number N, a symbol representing 1 is repeated N times. For example, the sequence (1; 1. 1 was the earliest revision that was widely adopted and led to what Microsoft designated the "Legacy-free PC". The Avogadro constant, commonly denoted N A or L, is an SI defining constant with an exact value of 6. In the context of species or mass transfer, the Péclet number is the product of the Reynolds number and the Schmidt number (Re × Sc). . The seven are 1 AD (I), 5 AD (V), 10 AD (X), 50 AD (L), 100 AD (C), 500 AD (D), and 1000 AD A prime number is a natural number that has exactly 2 divisors: 1 and itself. Regions are coloured by first digit. 5 is a centered tetrahedral number: 1, 5, 15, 35, 69, Every centered tetrahedral number with an index of 2, 3 or 4 modulo 5 is divisible by 5. [1] The series follows the lives of Los Angeles first responders : police officers , paramedics , firefighters , and dispatchers . The numbering of cardinals usually begins at zero, to accommodate the empty set. In 1993, The Football Association (The FA) switched to persistent squad numbers, abandoning the mandatory use of 1–11 for the starting line-up. The terms lakh or 1,00,000 (one hundred thousand, written as 100,000 in Pakistan, and outside the Indian subcontinent) and crore or 1,00,00,000 (ten million, written as 10,000,000 outside the subcontinent) are the most commonly used terms in Indian English to express large numbers in the system. These two numbers are called its divisors. The complete ISO 3166-1 list of countries and their assigned codes, listed in alphabetical order by the country's English short name used by the ISO 3166/MA: Each country's alpha-2 code is linked to more information about the assignment of its code elements. Written English has a large number of digraphs, such as ch , ea , oo , sh , and th . The English football champions are the winners of the top level league in English men's football, which since the 1992–93 season has been called the Premier League. 30 is an even, composite, pronic number. Neither USB 1. 5 is a centered square number: 1, 5, 13, 25, 41, An even number is an integer that is "evenly divisible" by two, that is divisible by two without remainder; an odd number is an integer that is not even. 414; 1. The word is derived from the early Italian millione (milione in modern Italian), from mille, "thousand", plus the augmentative suffix -one. A vehicle identification number (VIN; also called a chassis number or frame number) is a unique code, including a serial number, used by the automotive industry to identify individual motor vehicles, towed vehicles, motorcycles, scooters and mopeds, as defined by the The Mach number is named after the physicist and philosopher Ernst Mach according to a proposal by the aeronautical engineer Jakob Ackeret in 1929. The square of an imaginary number bi is −b 2. with an aliquot sum of 35; itself a semiprime, within an aliquot sequence (93,35,13,1,0) of three numbers to the Prime 13 in the 13-Aliquot tree. Type 1 diabetes makes up an estimated 5–10% of all diabetes cases. The number of binary strings of length n without an odd number of consecutive 1 s is the Fibonacci number F n+1. The unmodified term butanol usually refers to the straight chain isomer. The longest running number-one single of 1994 is "I'll Make Love to You" by Boyz II Men, which logged 14 weeks at number-one, tying the song with "I Will Always Love You" by Whitney Houston for the most weeks at number-one on the Billboard Hot 100 until "One Sweet Day" by Mariah Carey and Boyz II Men stayed atop the chart from December 1995 to 1973–1982; ATP ranking's average system as introduced on 23 August 1973. 93 is: the 28th distinct semiprime and the 9th of the form (3. Traditional British usage assigned new names for each power of one million (the long scale): 1,000,000 = 1 million; 1,000,000 2 = 1 billion; 1,000,000 3 = 1 trillion; and so on. It has minimal polynomial The Beatles topped the chart 17 times during the 1960s, more than any other act that decade Madonna is the most successful female solo artist in the UK, having achieved 13 number one singles Bryan Adams' first number one, "(Everything I Do) I Do It for You", spent 16 consecutive weeks at number one, longer than any other track Westlife were the BTS scored three number ones while Rodrigo, Justin Bieber, Drake and Lil Nas X scored two each, as the only acts to achieve multiple number-one songs in 2021. 4; 1. Aretha Franklin scored her first #1 hit with "Respect" in 1967. The longest running number-one single of 1981 is "Physical" by Olivia Newton-John which stayed at the top of the chart for six weeks in 1981 and then for four additional weeks in 1982, with a total of 10 weeks at number-one. [12] GS1 standards are developed and maintained through the GS1 Global Standards Management Process (GSMP), a community-based forum that brings together representatives from different industries and businesses. 1 (or variants), the top spot, or a song or album reaching the top spot, on any record chart; Number 1, a book by Billy Martin and Peter Golenbock; Rifle, Number 1, a British rifle; Ruger No. A number that is non-palindromic in all bases b in the range 2 ≤ b ≤ n − 2 can be called a strictly non-palindromic number. The golden ratio φ and its negative reciprocal −φ −1 are the two roots of the quadratic polynomial x 2 − x − 1. In linguistics, grammatical number is a feature of nouns, pronouns, adjectives and verb agreement that expresses count distinctions (such as "one", "two" or "three or more"). 1000 or one thousand is the natural number following 999 and preceding 1001. 355 × 10 17 seconds) old, and that the observable universe is 93 billion light years across (8. Numeral or number prefixes are prefixes derived from numerals or occasionally other numbers. 8 is the first number to be the aliquot sum of two numbers: the discrete semiprime 10 = 5 × 2, and squared prime 49 = 7 2. Liouville showed that this number belongs to a class of transcendental numbers that can be more closely approximated by rational numbers than can any irrational algebraic number, and this class of numbers are called Liouville Cuban primes of the form (x 3 - y 3) / (x - y), x is y + 1: . 7, 19, 37, 61, 127, 271, 331, 397, 547, 631, 919, 1657, 1801, 1951, 2269, 2437, 2791, 3169, 3571, 4219 M = 15 The 15 perfect matchings of K 6 15 as the difference of two positive squares (in orange). Goliath challenged the Israelites twice a day for forty days before David defeated him (1 Samuel 17:16). 801 –873 AD), who formally developed the method to break ciphers. British Sign Language. [1] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding 54 as the sum of three positive squares. 4142; 1. The atomic number or nuclear charge number (symbol Z) of a chemical element is the charge number of an atomic nucleus. With 2, 3, and 5 as its prime factors, it is a regular number and the first sphenic number, the smallest of the form , where r is a prime greater than 3. ; the first number in the 3rd triplet of consecutive semiprimes, 93, 94, 95. Constructible number: A number representing a length that can be constructed using a compass and straightedge. " 30 is a square pyramidal number. The numbers from 1 to 100 in English - Chart and ESOL Video with pronunciation of each number. The main victory at that time was with 7 correct results and the smallest victory with three actual and one additional number, the number of which was reduced from three to two. Number theory (or arithmetic or higher arithmetic in older usage) is a branch of pure mathematics devoted primarily to the study of the integers and arithmetic functions. For example, the number 6 is written as "110" in base 2, "20" in base 3, and "12" in base 4, none of which are palindromes. 2 2015–2019: Continued success, expansions in Southeast Asia 1. The number is now written as 1-212-736-5000. The second highest number is in While the exact number of deaths is unknown, the International Association of Genocide Scholars estimates around 1. 41421; ), where each term adds a digit of the decimal expansion of the positive square root of 2, is Cauchy but it does not converge to a rational number (in the real numbers, in contrast, it converges to the positive square root of 2). In ancient China, values for π included 3. In conventions of sign where zero is considered neither positive nor negative, 1 is the Most commonly, length is based on orthography (conventional spelling rules) and counting the number of written letters. This sequence goes on forever. Isomers of 1-butanol are isobutanol, butan-2-ol and tert-butanol. For example, out of the 16 binary strings of length 4, there are F 5 = 5 without an odd number of consecutive 1 s—they are 0000, 0011, 0110, 1100, 1111. For example, the current Big Bang model suggests that the universe is 13. A prime number is a number with only two divisors: 1 and itself. All of these power of ten numbers in the decimal number system use just the symbol "1" and the symbol "0". For ordinary nuclei composed of protons and neutrons , this is equal to the proton number ( n p ) or the number of protons found in the nucleus of every atom of that element. Square numbers: If =, then is a square. 1. 100,000,000 (one hundred million) is the natural number following 99,999,999 and preceding 100,000,001. 46x: Join (discontinued mobile phone service provider) 47x: Proximus (or other) 48x Elizabeth I (7 September 1533 – 24 March 1603) was Queen of England and Ireland from 17 November 1558 until her death in 1603. 15 is: The eighth composite number and the sixth semiprime and the first odd and fourth discrete semiprime; its proper divisors are 1, 3, and 5, so the first of the form (3. American singer Olivia Rodrigo reigned atop the chart for nine weeks, with two singles that debuted at number-one, " Drivers License " and " Good 4 U ", both from her debut studio album The symbol # is known variously in English-speaking regions as the number sign, hash, or pound sign. q), where q is a higher prime. These are the Billboard Hot 100 number-one hits of 1981. followed by any other, shorter number, like 32 51 724859, this is the number of a normal phone, not a mobile. The profit categories were changed, for example, from the 2011 round 41. Gloria Gaynor scored a #1 hit with "I Will Survive" in 1979. , a specific atomic number, or Z). It is one of only seven years to use just one Roman numeral. [269] [272] The government of Turkey continues to deny the genocide to the present day, arguing that those who died were victims of inter-ethnic fighting, famine, or disease during World War I; these claims are rejected In other words, the n th digit of this number is 1 only if n is one of the numbers 1! = 1, 2! = 2, 3! = 6, 4! = 24, etc. 1 was released in August 1998. It is the base of the natural logarithm function. qx ns hq xn yk zm fr sj ku ua