638768931 has 16 divisors (see below), whose sum is σ = 911930400. Its totient is φ = 396290048.

The previous prime is 638768929. The next prime is 638768953. The reversal of 638768931 is 139867836.

It is a cyclic number.

It is not a de Polignac number, because 638768931 - 2¹ = 638768929 is a prime.

It is a super-2 number, since 2×638768931² = 816051494421765522, which contains 22 as substring.

It is a Smith number, since the sum of its digits (51) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Harshad number since it is a multiple of its sum of digits (51).

It is not an unprimeable number, because it can be changed into a prime (638768131) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 65826 + ... + 74903.

It is an arithmetic number, because the mean of its divisors is an integer number (56995650).

Almost surely, 2^638768931 is an apocalyptic number.

638768931 is a deficient number, since it is larger than the sum of its proper divisors (273161469).

638768931 is a wasteful number, since it uses less digits than its factorization.

638768931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 140838.

The product of its digits is 1306368, while the sum is 51.

The square root of 638768931 is about 25273.8784320887. The cubic root of 638768931 is about 861.2209676464.

The spelling of 638768931 in words is "six hundred thirty-eight million, seven hundred sixty-eight thousand, nine hundred thirty-one".