639438956 has 24 divisors (see below), whose sum is σ = 1220358720. Its totient is φ = 291388032.

The previous prime is 639438949. The next prime is 639438959. The reversal of 639438956 is 659834936.

It is a Smith number, since the sum of its digits (53) coincides with the sum of the digits of its prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 639438898 and 639438907.

It is not an unprimeable number, because it can be changed into a prime (639438959) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 73721 + ... + 81936.

It is an arithmetic number, because the mean of its divisors is an integer number (50848280).

Almost surely, 2^639438956 is an apocalyptic number.

It is an amenable number.

639438956 is a deficient number, since it is larger than the sum of its proper divisors (580919764).

639438956 is a wasteful number, since it uses less digits than its factorization.

639438956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 155753 (or 155751 counting only the distinct ones).

The product of its digits is 4199040, while the sum is 53.

The square root of 639438956 is about 25287.1302444544. The cubic root of 639438956 is about 861.5219830893.

The spelling of 639438956 in words is "six hundred thirty-nine million, four hundred thirty-eight thousand, nine hundred fifty-six".