638840 has 16 divisors (see below), whose sum is σ = 1437480. Its totient is φ = 255520.

The previous prime is 638839. The next prime is 638857. The reversal of 638840 is 48836.

It is a congruent number.

It is an unprimeable number.

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, 7946 + ... + 8025.

2⁶³⁸⁸⁴⁰ is an apocalyptic number.

It is an amenable number.

638840 is an abundant number, since it is smaller than the sum of its proper divisors (798640).

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

638840 is a wasteful number, since it uses less digits than its factorization.

638840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15982 (or 15978 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 29.

The square root of 638840 is about 799.2746711863. The cubic root of 638840 is about 86.1252906083.

The spelling of 638840 in words is "six hundred thirty-eight thousand, eight hundred forty".