This is adynamic list and may never be able to satisfy particular standards for completeness. You can help byediting the page to add missing items, with references toreliable sources.
This is a list of notablenumbers and articles about them. The list does not contain all numbers in existence as most of thenumber sets are infinite. Numbers may be included in the list based on their mathematical, historical or cultural notability, but all numbers have qualities that could arguably make them notable. Even the smallest "uninteresting" number is paradoxically interesting for that very property. This is known as theinteresting number paradox.
The definition of what is classed as a number is rather diffuse and based on historical distinctions. For example, the pair of numbers (3,4) is commonly regarded as a number when it is in the form of acomplex number (3+4i), but not when it is in the form of avector (3,4). This list will also be categorized with the standard convention oftypes of numbers.
This list focuses on numbers asmathematical objects and isnot a list ofnumerals, which are linguistic devices: nouns, adjectives, or adverbs thatdesignate numbers. The distinction is drawn between thenumber five (anabstract object equal to 2+3), and thenumeral five (thenoun referring to the number).
Natural numbers are a subset of the integers and are of historical and pedagogical value as they can be used forcounting and often have ethno-cultural significance (see below). Beyond this, natural numbers are widely used as a building block for other number systems including theintegers,rational numbers andreal numbers. Natural numbers are those used forcounting (as in "there aresix (6) coins on the table") andordering (as in "this is thethird (3rd) largest city in the country"). In common language, words used for counting are "cardinal numbers" and words used for ordering are "ordinal numbers". Defined by thePeano axioms, the natural numbers form an infinitely large set. Often referred to as "the naturals", the natural numbers are usually symbolised by a boldfaceN (orblackboard bold, UnicodeU+2115ℕDOUBLE-STRUCK CAPITAL N).
The inclusion of0 in the set of natural numbers is ambiguous and subject to individual definitions. Inset theory andcomputer science, 0 is typically considered a natural number. Innumber theory, it usually is not. The ambiguity can be solved with the terms "non-negative integers", which includes 0, and "positive integers", which does not.
Natural numbers may have properties specific to the individual number or may be part of a set (such as prime numbers) of numbers with a particular property.
List of mathematically significant natural numbers
1, the multiplicative identity. Also the only natural number (not including 0) that is not prime or composite.
2, the base of thebinary number system, used in almost all modern computers and information systems. Also the only natural even number to also be prime.
3, 22-1, the firstMersenne prime and firstFermat number. It is the first odd prime, and it is also the 2 bit integer maximum value.
5, the sum of the first two primes and only prime which is the sum of 2 consecutive primes. The ratio of the length from the side to a diagonal of a regular pentagon is thegolden ratio.
6, the first of the series ofperfect numbers, whose proper factors sum to the number itself.
255, 28 − 1, the smallestperfect totient number that is neither a power of three nor thrice a prime; it is also the largest number that can be represented using an8-bit unsignedinteger.
1729, theHardy–Ramanujan number, also known as the secondtaxicab number; that is, the smallest positive integer that can be written as the sum of two positive cubes in two different ways.[1]
Along with their mathematical properties, many integers havecultural significance[2] or are also notable for their use in computing and measurement. As mathematical properties (such as divisibility) can confer practical utility, there may be interplay and connections between the cultural or practical significance of an integer and its mathematical properties.
List of integers notable for their cultural meanings
40, considered a significant number inTengrism and Turkish folklore. Multiple customs, such as those relating to how many days one must visit someone after a death in the family, include the number forty.
42, the "answer to the ultimate question of life, the universe, and everything" in the popular 1979 science fiction workThe Hitchhiker's Guide to the Galaxy.
65535, 216 − 1, the maximum value of a16-bit unsigned integer.
65536, 216, the number of possible16-bit combinations.
65537, 216 + 1, the most popular RSA public key prime exponent in most SSL/TLS certificates on the Web/Internet.
16777216, 224, or 166; the hexadecimal "million" (0x1000000), and the total number of possible color combinations in 24/32-bitTrue Color computer graphics.
Subsets of the natural numbers, such as the prime numbers, may be grouped into sets, for instance based on the divisibility of their members. Infinitely many such sets are possible. A list of notable classes of natural numbers may be found atclasses of natural numbers.
A highly composite number (HCN) is a positive integer with more divisors than any smaller positive integer. They are often used ingeometry, grouping and time measurement.
The integers are aset of numbers commonly encountered inarithmetic andnumber theory. There are manysubsets of the integers, including thenatural numbers,prime numbers,perfect numbers, etc. Many integers are notable for their mathematical properties. Integers are usually symbolised by a boldfaceZ (orblackboard bold, UnicodeU+2124ℤDOUBLE-STRUCK CAPITAL Z); this became the symbol for the integers based on the German word for "numbers" (Zahlen).
Notable integers include−1, the additive inverse of unity, and0, theadditive identity.
As with the natural numbers, the integers may also have cultural or practical significance. For instance,−40 is the equal point in theFahrenheit andCelsius scales.
SI prefixes
One important use of integers is inorders of magnitude. Apower of 10 is a number 10k, wherek is an integer. For instance, withk = 0, 1, 2, 3, ..., the appropriate powers of ten are 1, 10, 100, 1000, ... Powers of ten can also be fractional: for instance,k = -3 gives 1/1000, or 0.001. This is used inscientific notation, real numbers are written in the formm × 10n. The number 394,000 is written in this form as 3.94 × 105.
Integers are used asprefixes in theSI system. Ametric prefix is aunit prefix that precedes a basic unit of measure to indicate amultiple orfraction of the unit. Each prefix has a unique symbol that is prepended to the unit symbol. The prefixkilo-, for example, may be added togram to indicatemultiplication by one thousand: one kilogram is equal to one thousand grams. The prefixmilli-, likewise, may be added tometre to indicatedivision by one thousand; one millimetre is equal to one thousandth of a metre.
A rational number is any number that can be expressed as thequotient orfractionp/q of twointegers, anumeratorp and a non-zerodenominatorq.[5] Sinceq may be equal to 1, every integer is trivially a rational number. Theset of all rational numbers, often referred to as "the rationals", the field of rationals or the field of rational numbers is usually denoted by a boldfaceQ (orblackboard bold, UnicodeU+211AℚDOUBLE-STRUCK CAPITAL Q);[6] it was thus denoted in 1895 byGiuseppe Peano afterquoziente, Italian for "quotient".
Rational numbers such as 0.12 can be represented ininfinitely many ways, e.g.zero-point-one-two (0.12),three twenty-fifths (3/25),nine seventy-fifths (9/75), etc. This can be mitigated by representing rational numbers in a canonical form as an irreducible fraction.
A list of rational numbers is shown below. The names of fractions can be found atnumeral (linguistics).
Table of notable rational numbers
Decimal expansion
Fraction
Notability
1.0
1/1
One is the multiplicative identity. One is a rational number, as it is equal to 1/1.
One half occurs commonly in mathematical equations and in real world proportions. One half appears in the formula for the area of a triangle:1/2 × base × perpendicular height and in the formulae forfigurate numbers, such astriangular numbers andpentagonal numbers.
3.142 857...
22/7
A widely used approximation for the number. It can beproven that this number exceeds.
0.166 666...
1/6
One sixth. Often appears in mathematical equations, such as in thesum of squares of the integers and in the solution to the Basel problem.
Real numbers
Real numbers are least upper bounds of sets of rational numbers that are bounded above, or greatest lower bounds of sets of rational numbers that are bounded below, or limits of convergent sequences of rational numbers. Real numbers that are not rational numbers are calledirrational numbers. The real numbers are categorised as algebraic numbers (which are the root of a polynomial with rational coefficients) or transcendental numbers, which are not; all rational numbers are algebraic.
(cannot be written as expressions involving integers and the operations of addition, subtraction, multiplication, division, and the extraction of roots)
1.303577269034296391257099112153
Defined as the unique positive real root of a certain polynomial of degree 71. The limit ratio between subsequent numbers in the binaryLook-and-say sequence (OEIS: A014715).
The only real solution of.(OEIS: A058265) The limit ratio between subsequent numbers in theTribonacci sequence.(OEIS: A000073) Appears in the volume and coordinates of thesnub cube and some related polyhedra.
Some numbers are known to beirrational numbers, but have not been proven to be transcendental. This differs from the algebraic numbers, which are known not to be transcendental.
Real but not known to be irrational, nor transcendental
For some numbers, it is not known whether they are algebraic or transcendental. The following list includes real numbers that have not been proved to be irrational, nor transcendental.
Believed to be transcendental but not proven to be so. However, it was shown that at least one of and the Euler-Gompertz constant is transcendental.[19][20] It was also shown that all but at most one number in an infinite list containing have to be transcendental.[21][22]
Many languages have words expressingindefinite and fictitious numbers—inexact terms of indefinite size, used for comic effect, for exaggeration, asplaceholder names, or when precision is unnecessary or undesirable. One technical term for such words is "non-numerical vague quantifier".[45] Such words designed to indicate large quantities can be called "indefinite hyperbolic numerals".[46]
^Ayonrinde, Oyedeji A.; Stefatos, Anthi; Miller, Shadé; Richer, Amanda; Nadkarni, Pallavi; She, Jennifer; Alghofaily, Ahmad; Mngoma, Nomusa (2020-06-12). "The salience and symbolism of numbers across cultural beliefs and practice".International Review of Psychiatry.33 (1–2):179–188.doi:10.1080/09540261.2020.1769289.ISSN0954-0261.PMID32527165.S2CID219605482.
^André-Jeannin, Richard; 'Irrationalité de la somme des inverses de certaines suites récurrentes.';Comptes Rendus de l'Académie des Sciences - Series I - Mathematics, vol. 308, issue 19 (1989), pp. 539-541.
^S. Kato, 'Irrationality of reciprocal sums of Fibonacci numbers', Master's thesis, Keio Univ. 1996
^Nesterenko, Yu. V. (January 2016), "On Catalan's constant",Proceedings of the Steklov Institute of Mathematics,292 (1):153–170,doi:10.1134/s0081543816010107,S2CID124903059