Forty-seven

The forty-seven (47) is the natural number that follows 46 and precedes 48.

Math

• It's the 15th prime number, after 43rd and before 53rd.
• It is a number of Keith, since if it is based on his digits decimals a sequence similar to that of Fibonacci, the number itself uses: 4, 7, 11, 18, 29, 47...
• A prime number of Thabit and as such is related to the pair of friends numbers (17296, 18416).
• It's a prime number of Lucas.
• He's an Eisenstein cousin with no imaginary part and a real part of form 3 n - 1.

Chemistry

• 47 is the atomic number of silver (Ag).

Astronomy

• The 47-year cycle of Mars: after 47 years, 22 synodic periods of 780 days each, Mars returns to the same position between the stars and is in the same relationship with the Earth and the Sun. The ancient Mesopotamians discovered this cycle.
• Messier M47 is an open cluster in the Puppis constellation.
• Astronomical object of the New General Catalogue NGC 47 is a barred spiral galaxy located in the constellation of Cetus.