639903728 has 20 divisors (see below), whose sum is σ = 1270054128. Its totient is φ = 312147840.

The previous prime is 639903727. The next prime is 639903743. The reversal of 639903728 is 827309936.

It is a super-2 number, since 2×639903728² = 818953562216595968, which contains 22 as substring.

It is a Smith number, since the sum of its digits (47) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639903727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 487076 + ... + 488387.

Almost surely, 2^639903728 is an apocalyptic number.

It is an amenable number.

639903728 is a deficient number, since it is larger than the sum of its proper divisors (630150400).

639903728 is a wasteful number, since it uses less digits than its factorization.

639903728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 975512 (or 975506 counting only the distinct ones).

The product of its (nonzero) digits is 489888, while the sum is 47.

The square root of 639903728 is about 25296.3184673185. The cubic root of 639903728 is about 861.7306630675.

The spelling of 639903728 in words is "six hundred thirty-nine million, nine hundred three thousand, seven hundred twenty-eight".