forty-seven

Forty-seven is the fifteenth prime number, a safe prime, the thirteenth super-singular 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 a Lucas 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 also a Keith number.

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.