638909680 has 20 divisors (see below), whose sum is σ = 1485465192. Its totient is φ = 255563840.

The previous prime is 638909629. The next prime is 638909717. The reversal of 638909680 is 86909836.

638909680 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3993106 + ... + 3993265.

Almost surely, 2^638909680 is an apocalyptic number.

It is an amenable number.

638909680 is an abundant number, since it is smaller than the sum of its proper divisors (846555512).

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

638909680 is a wasteful number, since it uses less digits than its factorization.

638909680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7986384 (or 7986378 counting only the distinct ones).

The product of its (nonzero) digits is 559872, while the sum is 49.

The square root of 638909680 is about 25276.6627544065. The cubic root of 638909680 is about 861.2842180030.

The spelling of 638909680 in words is "six hundred thirty-eight million, nine hundred nine thousand, six hundred eighty".