638691478057 has 2 divisors, whose sum is σ = 638691478058. Its totient is φ = 638691478056.

The previous prime is 638691478013. The next prime is 638691478079. The reversal of 638691478057 is 750874196836.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 433100874816 + 205590603241 = 658104^2 + 453421^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-638691478057 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 638691478057.

It is not a weakly prime, because it can be changed into another prime (638691478097) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319345739028 + 319345739029.

It is an arithmetic number, because the mean of its divisors is an integer number (319345739029).

Almost surely, 2^638691478057 is an apocalyptic number.

It is an amenable number.

638691478057 is a deficient number, since it is larger than the sum of its proper divisors (1).

638691478057 is an equidigital number, since it uses as much as digits as its factorization.

638691478057 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 60963840, while the sum is 64.

The spelling of 638691478057 in words is "six hundred thirty-eight billion, six hundred ninety-one million, four hundred seventy-eight thousand, fifty-seven".