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 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 because the only ways ...

In mathematics

Forty-seven is the fifteenth prime number, a

safe prime In number theory, a prime number ''p'' is a if 2''p'' + 1 is also prime. The number 2''p'' + 1 associated with a Sophie Germain prime is called a . For example, 11 is a Sophie Germain prime and 2 × 11 + ...

, the thirteenth supersingular prime, the fourth isolated prime, and the sixth

Lucas prime The Lucas numbers or Lucas series are an integer sequence named after the mathematician François Édouard Anatole Lucas (1842–1891), who studied both that sequence and the closely related Fibonacci numbers. Lucas numbers and Fibonacci nu ...

. Forty-seven is a highly cototient number. It is an

Eisenstein prime In mathematics, an Eisenstein prime is an Eisenstein integer : z = a + b\,\omega, \quad \text \quad \omega = e^, that is irreducible (or equivalently prime) in the ring-theoretic sense: its only Eisenstein divisors are the units , itself ...

with no imaginary part and real part of the form . It is a

Lucas number The Lucas numbers or Lucas series are an integer sequence named after the mathematician François Édouard Anatole Lucas (1842–1891), who studied both that sequence and the closely related Fibonacci numbers. Lucas numbers and Fibonacci n ...

. It is also a Keith number 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 In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are u ...

on 9 unlabeled nodes. Forty-seven is a strictly non-palindromic number. Its representation in binary being 101111, 47 is a prime

Thabit number In number theory, a Thabit number, Thâbit ibn Qurra number, or 321 number is an integer of the form 3 \cdot 2^n - 1 for a non-negative integer ''n''. The first few Thabit numbers are: : 2, 5, 11, 23, 47, 95, 191, 383, 767, 1535, 3071, 61 ...

, and as such is related to the pair of

amicable number Amicable numbers are two different natural numbers related in such a way that the sum of the proper divisors of each is equal to the other number. That is, σ(''a'')=''b'' and σ(''b'')=''a'', where σ(''n'') is equal to the sum of positive d ...

s .

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 every ...

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 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 The history of Mesopotamia ranges from the earliest human occupation in the Paleolithic period up to Late antiquity. This history is pieced together from evidence retrieved from archaeological excavations and, after the introduction of writing i ...

discovered this cycle. *

Messier object The Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his ''Catalogue des Nébuleuses et des Amas d'Étoiles'' (''Catalogue of Nebulae and Star Clusters''). Because Messier was only in ...

M47, a

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

4.5 open cluster in the constellation Puppis * 47 Tucanae, the second brightest globular cluster in the sky, located in the constellation Tucana. * The New General Catalogue object NGC 47,The NGC / IC Project – Home of the Historically Corrected New General Catalogue (HCNGC) since 1993
/ref> a

barred spiral galaxy A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars. Bars are found in about two thirds of all spiral galaxies, and generally affect both the motions of stars and interstellar gas within spiral galaxies ...

in the constellation

Cetus Cetus () is a constellation, sometimes called 'the whale' in English. The Cetus was a sea monster in Greek mythology which both Perseus and Heracles needed to slay. Cetus is in the region of the sky that contains other water-related constellat ...

. This object is also designated as NGC 58.

In popular culture

Pomona College

Calendar years

47 BC __NOTOC__ Year 47 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Consulship of Calenius and Vatinius (or, less frequently, year 707 ''Ab urbe condita''). The denomination 47 BC for this year has been ...

* AD 47

Other

* Telephone dialing country code for

Norway Norway, officially the Kingdom of Norway, is a 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 Jan Mayen and the ...

*The

AK-47 The AK-47, officially known as the ''Avtomat Kalashnikova'' (; also known as the Kalashnikov or just AK), is a gas-operated assault rifle that is chambered for the 7.62×39mm cartridge. Developed in the Soviet Union by Russian small-arms d ...

, 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-bom ...

was a fighter plane in World War II. * There are Forty-seven Ronin 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''), two ...

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

Agent 47 Agent 47 is a fictional character, the protagonist and the player character of the ''Hitman'' video game franchise, developed by IO Interactive. He has been featured in all games of the series, as well as various spin-off media, including two t ...

References

{{Integers, zero Integers In-jokes