639745924 has 6 divisors (see below), whose sum is σ = 1119555374. Its totient is φ = 319872960.

The previous prime is 639745913. The next prime is 639745927. The reversal of 639745924 is 429547936.

It can be written as a sum of positive squares in only one way, i.e., 523494400 + 116251524 = 22880^2 + 10782^2 .

It is a super-2 number, since 2×639745924² = 818549694549227552, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (639745927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 79968237 + ... + 79968244.

Almost surely, 2^639745924 is an apocalyptic number.

It is an amenable number.

639745924 is a deficient number, since it is larger than the sum of its proper divisors (479809450).

639745924 is a wasteful number, since it uses less digits than its factorization.

639745924 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 159936485 (or 159936483 counting only the distinct ones).

The product of its digits is 1632960, while the sum is 49.

The square root of 639745924 is about 25293.1991649929. The cubic root of 639745924 is about 861.6598213042.

The spelling of 639745924 in words is "six hundred thirty-nine million, seven hundred forty-five thousand, nine hundred twenty-four".