638400904 has 16 divisors (see below), whose sum is σ = 1200268800. Its totient is φ = 318329232.

The previous prime is 638400899. The next prime is 638400907. The reversal of 638400904 is 409004836.

It is a self number, because there is not a number n which added to its sum of digits gives 638400904.

It is not an unprimeable number, because it can be changed into a prime (638400907) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 105784 + ... + 111655.

It is an arithmetic number, because the mean of its divisors is an integer number (75016800).

Almost surely, 2^638400904 is an apocalyptic number.

It is an amenable number.

638400904 is a deficient number, since it is larger than the sum of its proper divisors (561867896).

638400904 is a wasteful number, since it uses less digits than its factorization.

638400904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 217812 (or 217808 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 34.

The square root of 638400904 is about 25266.5966050040. The cubic root of 638400904 is about 861.0555382588.

The spelling of 638400904 in words is "six hundred thirty-eight million, four hundred thousand, nine hundred four".