638690990 has 48 divisors (see below), whose sum is σ = 1365844032. Its totient is φ = 214312896.

The previous prime is 638690981. The next prime is 638691007. The reversal of 638690990 is 99096836.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 9164 + ... + 36896.

It is an arithmetic number, because the mean of its divisors is an integer number (28455084).

Almost surely, 2^638690990 is an apocalyptic number.

638690990 is an abundant number, since it is smaller than the sum of its proper divisors (727153042).

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

638690990 is a wasteful number, since it uses less digits than its factorization.

638690990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27801 (or 27794 counting only the distinct ones).

The product of its (nonzero) digits is 629856, while the sum is 50.

The square root of 638690990 is about 25272.3364570829. The cubic root of 638690990 is about 861.1859382065.

The spelling of 638690990 in words is "six hundred thirty-eight million, six hundred ninety thousand, nine hundred ninety".