638940864 has 112 divisors (see below), whose sum is σ = 1770022368. Its totient is φ = 203194368.

The previous prime is 638940853. The next prime is 638940871. The reversal of 638940864 is 468049836.

It is a Harshad number since it is a multiple of its sum of digits (48).

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 15 ways as a sum of consecutive naturals, for example, 375664 + ... + 377360.

Almost surely, 2^638940864 is an apocalyptic number.

638940864 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 638940864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (885011184).

638940864 is an abundant number, since it is smaller than the sum of its proper divisors (1131081504).

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

638940864 is a wasteful number, since it uses less digits than its factorization.

638940864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1802 (or 1792 counting only the distinct ones).

The product of its (nonzero) digits is 995328, while the sum is 48.

The square root of 638940864 is about 25277.2796004633. The cubic root of 638940864 is about 861.2982303384.

The spelling of 638940864 in words is "six hundred thirty-eight million, nine hundred forty thousand, eight hundred sixty-four".