640904400 has 300 divisors, whose sum is σ = 2333061984. Its totient is φ = 168480000.

The previous prime is 640904399. The next prime is 640904443. The reversal of 640904400 is 4409046.

It is a tau number, because it is divible by the number of its divisors (300).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 4244325 + ... + 4244475.

Almost surely, 2^640904400 is an apocalyptic number.

640904400 is a gapful number since it is divisible by the number (60) 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 640904400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1166530992).

640904400 is an abundant number, since it is smaller than the sum of its proper divisors (1692157584).

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

640904400 is a wasteful number, since it uses less digits than its factorization.

640904400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 312 (or 292 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 640904400 is about 25316.0897454563. The cubic root of 640904400 is about 862.1796163550.

The spelling of 640904400 in words is "six hundred forty million, nine hundred four thousand, four hundred".