638625857 has 2 divisors, whose sum is σ = 638625858. Its totient is φ = 638625856.

The previous prime is 638625851. The next prime is 638625887. The reversal of 638625857 is 758526836.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 456078736 + 182547121 = 21356^2 + 13511^2 .

It is a cyclic number.

It is not a de Polignac number, because 638625857 - 2⁸ = 638625601 is a prime.

It is not a weakly prime, because it can be changed into another prime (638625851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319312928 + 319312929.

It is an arithmetic number, because the mean of its divisors is an integer number (319312929).

Almost surely, 2^638625857 is an apocalyptic number.

It is an amenable number.

638625857 is a deficient number, since it is larger than the sum of its proper divisors (1).

638625857 is an equidigital number, since it uses as much as digits as its factorization.

638625857 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2419200, while the sum is 50.

The square root of 638625857 is about 25271.0478017830. The cubic root of 638625857 is about 861.1566629485.

The spelling of 638625857 in words is "six hundred thirty-eight million, six hundred twenty-five thousand, eight hundred fifty-seven".