644688400 has 60 divisors (see below), whose sum is σ = 1598857984. Its totient is φ = 249552000.

The previous prime is 644688377. The next prime is 644688403. The reversal of 644688400 is 4886446.

It is a Harshad number since it is a multiple of its sum of digits (40).

It is not an unprimeable number, because it can be changed into a prime (644688403) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 13596 + ... + 38395.

Almost surely, 2^644688400 is an apocalyptic number.

It is an amenable number.

644688400 is an abundant number, since it is smaller than the sum of its proper divisors (954169584).

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

644688400 is a wasteful number, since it uses less digits than its factorization.

644688400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52040 (or 52029 counting only the distinct ones).

The product of its (nonzero) digits is 147456, while the sum is 40.

The square root of 644688400 is about 25390.7148383026. The cubic root of 644688400 is about 863.8731023623.

The spelling of 644688400 in words is "six hundred forty-four million, six hundred eighty-eight thousand, four hundred".