47
47 (forty-seven) is the natural number following 46 and preceding 48.
Forty-seven is the fifteenth prime number, a safe prime, the thirteenth supersingular prime, and the sixth Lucas prime. Forty-seven is a highly cototient number. It is an Eisenstein prime with no imaginary part and real part of the form 3n − 1.
It is also a Keith number, because it recurs in a Fibonacci-like sequence started from its base 10 digits: 4, 7, 11, 18, 29, 47….
Forty-seven is a strictly non-palindromic number.
Its representation in binary being 00101111, 47 is a prime Thabit number, and as such is related to the pair of amicable numbers {17296, 18416}.
Forty-seven is a Carol number. It is a real prime number.
The atomic number of silver is 47.
Messier object M47, a magnitude 4.5 open cluster in the constellation Puppis.
The New General Catalogue object NGC 47, a barred spiral galaxy in the constellation Cetus.
This object is also designated as NGC 58.
The Saros number of the solar eclipse series which began in April of 1306 BC and ended in May of 26 BC.[2]
The duration of Saros series 47 was 1280.1 years, and it contained 72 solar eclipses.
The Saros number of the lunar eclipse series which began in July of 1275 BC and ended in February AD 258.[3] The duration of Saros series 47 was 1537.5 years, and it contained 86 lunar eclipses.
Forty-seven has been the favorite number of Pomona College, California, USA, since 1964. A mathematical proof, written in 1964 by Professor Donald Bentley, supposedly demonstrates that all numbers are equal to 47.
However, Bentley offered it as a "joke proof" further to a popular student research project that listed real and imaginative "47 sightings". Bentley used the invalid proof to introduce his students to the concept of mathematical proofs.
The 47 society is an outgrowth of the "movement" started at Pomona College. They explore the belief that 47 occurs in nature more frequenly than other numbers and share their personal sightings
in consideration of 47 being "the quintessential random number".
