639887631 has 4 divisors (see below), whose sum is σ = 853183512. Its totient is φ = 426591752.

The previous prime is 639887617. The next prime is 639887653. The reversal of 639887631 is 136788936.

639887631 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 639887631 - 2⁹ = 639887119 is a prime.

It is a super-2 number, since 2×639887631² = 818912360613584322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639887431) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 106647936 + ... + 106647941.

It is an arithmetic number, because the mean of its divisors is an integer number (213295878).

Almost surely, 2^639887631 is an apocalyptic number.

639887631 is a deficient number, since it is larger than the sum of its proper divisors (213295881).

639887631 is a wasteful number, since it uses less digits than its factorization.

639887631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 213295880.

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

The square root of 639887631 is about 25296.0002964896. Note that the first 3 decimals coincide. The cubic root of 639887631 is about 861.7234372958.

The spelling of 639887631 in words is "six hundred thirty-nine million, eight hundred eighty-seven thousand, six hundred thirty-one".