639538856 has 64 divisors (see below), whose sum is σ = 1364299200. Its totient is φ = 278387200.

The previous prime is 639538831. The next prime is 639538883. The reversal of 639538856 is 658835936.

It is a junction number, because it is equal to n+sod(n) for n = 639538798 and 639538807.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 333356 + ... + 335268.

It is an arithmetic number, because the mean of its divisors is an integer number (21317175).

Almost surely, 2^639538856 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639538856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (682149600).

639538856 is an abundant number, since it is smaller than the sum of its proper divisors (724760344).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

639538856 is a wasteful number, since it uses less digits than its factorization.

639538856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2090 (or 2086 counting only the distinct ones).

The product of its digits is 4665600, while the sum is 53.

The square root of 639538856 is about 25289.1054804238. The cubic root of 639538856 is about 861.5668461491.

The spelling of 639538856 in words is "six hundred thirty-nine million, five hundred thirty-eight thousand, eight hundred fifty-six".