638620638923257 has 2 divisors, whose sum is σ = 638620638923258. Its totient is φ = 638620638923256.

The previous prime is 638620638923161. The next prime is 638620638923317. The reversal of 638620638923257 is 752329836026836.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 636528881266576 + 2091757656681 = 25229524^2 + 1446291^2 .

It is a cyclic number.

It is not a de Polignac number, because 638620638923257 - 2⁷ = 638620638923129 is a prime.

It is not a weakly prime, because it can be changed into another prime (638620638923957) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319310319461628 + 319310319461629.

It is an arithmetic number, because the mean of its divisors is an integer number (319310319461629).

Almost surely, 2^{638620638923257} is an apocalyptic number.

It is an amenable number.

638620638923257 is a deficient number, since it is larger than the sum of its proper divisors (1).

638620638923257 is an equidigital number, since it uses as much as digits as its factorization.

638620638923257 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 940584960, while the sum is 70.

The spelling of 638620638923257 in words is "six hundred thirty-eight trillion, six hundred twenty billion, six hundred thirty-eight million, nine hundred twenty-three thousand, two hundred fifty-seven".