638620638923957 has 2 divisors, whose sum is σ = 638620638923958. Its totient is φ = 638620638923956.

The previous prime is 638620638923903. The next prime is 638620638923983. The reversal of 638620638923957 is 759329836026836.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 630612242656036 + 8008396267921 = 25111994^2 + 2829911^2 .

It is a cyclic number.

It is not a de Polignac number, because 638620638923957 - 2⁴⁶ = 568251894746293 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638620638923257) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319310319461978 + 319310319461979.

It is an arithmetic number, because the mean of its divisors is an integer number (319310319461979).

Almost surely, 2^{638620638923957} is an apocalyptic number.

It is an amenable number.

638620638923957 is a deficient number, since it is larger than the sum of its proper divisors (1).

638620638923957 is an equidigital number, since it uses as much as digits as its factorization.

638620638923957 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4232632320, while the sum is 77.

The spelling of 638620638923957 in words is "six hundred thirty-eight trillion, six hundred twenty billion, six hundred thirty-eight million, nine hundred twenty-three thousand, nine hundred fifty-seven".