This number is a prime.
Tyrannosauras rex measured up to 47 feet in overall length. [Norris]
In the Pixar Film Monsters Inc., the scream factory had enjoyed 47 accident-free days at the start of the movie. [Hartley]
There is an abnormally high use of the prime number 47 in episodes of Star Trek. For example, in the Star Trek: Voyager episode "Infinite Regress," Naomi Wildman reveals that there are 47 sub-orders of the Prime Directive.
The AK-47 is the most widespread weapon in the world. [Kalashnikov]
The beast number raised to power 47 has sum of digits equal to the beast number. [De Geest]
The MK-47 was the first and last Soviet calculator with magnetic cards. [Frolov]
47 is the first and only prime p less than 20000 of the form p*2^(p+1)-1, where p is prime. [Luhn]
Marine Storm Warnings occur with forecast winds greater than 47 knots. [NOAA]
The KJV Bible was translated by 47 scholars. [English]
"The number 47 may be a flying increment to fill allspace, to fill out the eight triangular facets of the non-allspace-filling vector equilibrium to form the allspace-filling first nuclear cube." (Quoted from section 1238.51 of Synergetics by R. Buckminster Fuller.) [Croll]
47 + 2 equals the reversal of 47 * 2.
It is approximately 47 degrees from the Tropic of Cancer (the greatest distance north that the sun can appear directly overhead) to the Tropic of Capricorn (the greatest distance south that the sun can appear directly overhead). [Obeidin]
Isaac Asimov's Book of Facts mentions the "fact" that mosquitoes have 47 teeth. [Patterson]
The gyroelongated pentagonal cupolarotunda has 47 faces. It is the largest prime number of faces a Johnson solid can have. [Hartley]
47 is the largest known number, n, such that n and n + 1 are both Ulam numbers. [McCranie]
The 47 Society is a humorous society at Pomona College in California that propagates the belief that the number 47 is the quintessential random number. Campus lore suggests that Pomona math professor Donald Bentley produced a convincing mathematical proof that 47 was equal to all other integers. (See www.47.net/47society/.) [Schuler]
There are an incredible number of references to the number 47 in the TV show Alias. [Hunt]
According to Chinese legend, a 16th century official named Wan Hu attempted a flight to the Moon by using two kites fastened to a sedan chair on which he had strapped 47 black powder rockets. 47 servants simultaneously lit the fuses and Wan Hu disappeared in a burst of flame and smoke. A crater on the far side of the Moon (at 9.8°S, 138.8°W) has been named in his honor. [Caldwell]
The surprising formula for primes proposed by J. Minac and C. Willans in 1995 had 47 symbols. This formula, based on Wilson theorem, gives all the primes successively and without repetition, but unfortunately is not very convenient. [Capelle]
The modern concert harp typically has 47 strings. [Kamath]
ceil((π + e/47)^47) is prime. [Noll]
Mary Mallon, better known as "Typhoid Mary," was a food service worker who infected 47 people with the bacterium Salmonella enterica typhi. She was the first "healthy carrier" of typhoid fever in the United States.
The Hadwiger problem asks for the largest number of subcubes (not necessarily different) into which a cube cannot be divided by plane cuts. The answer is 47. [Post]
The smallest prime whose number of perfect partitions is greater than itself. [Beedassy]
In the play The Five Hysterical Girls Theorem by Rinne Groff, renowned number theorist Moses Vazsonyi fears that he has lost his edge in the intellectually grueling world of prime number theory at the age of 47.
The first of two consecutive primes whose sum has the form 10n. [Silva]
There are 47 known Mersenne primes (as of 2011). (The 47th discovered is actually the 46th in size).
Henri Emile Benoit Matisse's painting "Le Bateau" hung for 47 days in the Museum of Modern Art, New York City, between October 18 and December 4, 1961, and not a single person noticed it was upside down.
The sum of the first six primes with distinct end-digits (11+2+3+5+7+19). [Silva]
The largest prime number whose square (2209) can be displayed on a 24-hour digital clock. [Fellows]
Over 47 years after it was first published, "Mastering the Art of French Cooking" by Julia Child finally topped the best-seller list. [Clifford]
The number of triangles in this figure.
The smallest prime of the only pair of two consecutive two-digit primes whose sum of the reversals is prime. [Silva]
The forty-seventh Fibonacci and Lucas numbers are both prime and are respectively 2971215073 and 6643838879. Forty-seven represents the largest subscript less than one hundred for which this is true. Among the first one hundred Fibonacci numbers and Lucas numbers, both are prime for the subscripts 4, 5, 7, 11, 13, 17, and 47. [Schiffman]
In 1981, Harry L. Nelson produced a 47-page printout containing the 206,545-digit solution to Archimedes' Cattle Problem. The number was generated from a CRAY-1 supercomputer at the Lawrence Livermore National Laboratory and was published in small type in the Journal of Recreational Mathematics.
47 is the last "totally safe" prime: 47 -> 23 -> 11 -> 5 -> 2 (complete descending sequence of safe primes till 2 is reached). [Wood]
Lavandula is a genus of 47 known species of flowering plants in the mint family, Lamiaceae. [McKenzie]
Euphemia Lofton Haynes, the first African-American woman to earn a Ph.D. in mathematics, devoted her life to education in the Washington, D.C. area for 47 years.
"47 Ways To Die" is the song heard over the opening and closing credits for the film "The Hit List", 2011, starring Cuba Gooding, Jr. [Green]
The only double-digit prime from which no one prime is obtained by inserting between its digits d d's (where d is any digit). [Loungrides]
The largest double-digit prime ab such that a^a + b^b is prime. [Loungrides]
In the CW show called The 100, the captives held at Mount Weather are referred to as "the 47." [Phillips]
(47, 53, 59, 61) is the only tetrad of successive double-digit primes p < q < r < s such that (p+q) divides r*s+1, i.e., (47+53) divides 59*61+1. [Loungrides]
The smaller of only two double-digit primes, whose cube, (103823), can be represented as the concatenation of two 3-digit primes. [Loungrides]
The sum of the first 47 positive integers with digits in strictly ascending order is divisible by 47 (2350/47=50). The next and largest such prime is 383 (1848741/383=4827). [Gaydos]
47 (exactly half) of the first 94 prime numbers each has at least one prime twin. [Gaydos]
The largest prime sum of digits among all known Mersenne prime exponents: sod(82589933) = 47. [Harrison]
German doctor Otto Heinrich Warburg was nominated for the Nobel Prize award 47 times over the course of his career. [Hess]
There were 47 people on White Island when a powerful volcanic eruption trapped tourists. [Linkous]
The famous 1728 Chambers' Cyclopedia is made up of 47 sections. [Olry]
47 squares are each adjacent to at least one distinct digit prime number. [Gaydos]
"47 Wide Right" was Scott Norwood's missed 47-yard field goal attempt for the Buffalo Bills at the end of Super Bowl XXV. [Williams]
The product of 47 and 4*7 is "perfect" if prime proper divisors are omitted (1+4+14+28+94+188+329+658).