47 (forty-seven) is the

natural number In mathematics, the natural numbers are those numbers used for counting (as in "there are ''six'' coins on the table") and ordering (as in "this is the ''third'' largest city in the country"). Numbers used for counting are called '' cardinal ...

following 46 and preceding 48. It is a

prime number A prime number (or a prime) is a natural number greater than 1 that is not a Product (mathematics), product of two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number. For example, 5 is prime ...

In mathematics

Forty-seven is the fifteenth prime number, a safe prime, the thirteenth supersingular prime, the fourth isolated prime, and the sixth Lucas prime. Forty-seven is a

highly cototient number In number theory, a branch of mathematics, a highly cototient number is a positive integer k which is above 1 and has more solutions to the equation :x - \phi(x) = k than any other integer below k and above 1. Here, \phi is Euler's totient f ...

. It is an Eisenstein prime with no imaginary part and real part of the form . It is a Lucas number. It is also a

Keith number In number theory, a Keith number or repfigit number (short for repetitive Fibonacci-like digit) is a natural number n in a given number base b with k digits such that when a sequence is created such that the first k terms are the k digits of n a ...

because its digits appear as successive terms earlier in the series of Lucas numbers: 2, 1, 3, 4, 7, 11, 18, 29, 47, ... It is the number of trees on 9 unlabeled nodes. Forty-seven is a strictly non-palindromic number. Its representation in binary being 101111, 47 is a prime Thabit number, and as such is related to the pair of amicable numbers .

In science

* 47 is the

atomic number The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of ever ...

silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...

Astronomy

* The 47-year cycle of

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...

: after 47 years – 22

synodic Synodic, may refer to: * Synodic day * Synodic month * Synodic orbital period, synodic year or synodic time, the time of an celestial object An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring ...

periods of 780 days each – Mars returns to the same position among the stars and is in the same relationship to the Earth and Sun. The ancient Mesopotamians discovered this cycle. * Messier object M47, a magnitude 4.5

open cluster An open cluster is a type of star cluster made of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, an ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the earliest constellation ...

Puppis Puppis is a constellation in the southern sky. Puppis, the Latin translation of "poop deck", was originally part of an over-large constellation Argo Navis (the ship of Jason and the Argonauts), which centuries after its initial description, wa ...

47 Tucanae 47 Tucanae, or 47 Tuc (also designated NGC 104) is a globular cluster located in the constellation Tucana. It is about away from Earth, and 120 light years in diameter. 47 Tuc can be seen with the naked eye, with an apparent magnitude of 4.1. ...

, the second brightest globular cluster in the sky, located in the constellation Tucana. * The

New General Catalogue The ''New General Catalogue of Nebulae and Clusters of Stars'' (abbreviated NGC) is an astronomical catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. The NGC contains 7,840 objects, including galaxies, star clusters and ...

object

NGC 47 NGC 47 (also known as NGC 58, MCG -1-1-55, IRAS00119-0726 and PGC 967) is a barred spiral galaxy in the constellation Cetus, discovered in 1886 by Ernst Wilhelm Leberecht Tempel. Its alternate name NGC 58 is due to the observation by Lewis Swift ...

,The NGC / IC Project – Home of the Historically Corrected New General Catalogue (HCNGC) since 1993
/ref> a barred spiral galaxy in the constellation Cetus. This object is also designated as

NGC 58 NGC 47 (also known as NGC 58, MCG -1-1-55, IRAS00119-0726 and PGC 967) is a barred spiral galaxy in the constellation Cetus, discovered in 1886 by Ernst Wilhelm Leberecht Tempel. Its alternate name NGC 58 is due to the observation by Lewis Swift ...

In popular culture

Pomona College

Calendar years

* 47 BC * AD 47

Other

* Telephone dialing country code for

Norway Norway, officially the Kingdom of Norway, is a Nordic countries, Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of ...

*The AK-47, also known as a Kalashnikov rifle, is one of the most widely used military weapons in the world. *The

CH-47 Chinook The Boeing CH-47 Chinook is a tandem rotor helicopter developed by American rotorcraft company Vertol and manufactured by Boeing Vertol. The Chinook is a heavy-lift helicopter that is among the heaviest lifting Western helicopters. Its name, C ...

, a helicopter. *47 is the number of the French department Lot-et-Garonne. *The

P-47 Thunderbolt The Republic P-47 Thunderbolt is a World War II-era fighter aircraft produced by the American company Republic Aviation from 1941 through 1945. It was a successful high-altitude fighter and it also served as the foremost American fighter-bomb ...

was a fighter plane in World War II. * There are

Forty-seven Ronin 47 (forty-seven) is the natural number following 46 and preceding 48. It is a prime number. In mathematics Forty-seven is the fifteenth prime number, a safe prime, the thirteenth supersingular prime, the fourth isolated prime, and the sixt ...

in the famous Japanese story. * There are 47

Prefectures of Japan Japan is divided into 47 prefectures (, ''todōfuken'', ), which rank immediately below the national government and form the country's first level of jurisdiction and administrative division. They include 43 prefectures proper (, '' ken''), tw ...

. * The player protagonist of the ''Hitman'' video game franchise is called Agent 47.

References

{{Integers, zero Integers In-jokes