644042900 has 18 divisors (see below), whose sum is σ = 1397573310. Its totient is φ = 257617120.

The previous prime is 644042897. The next prime is 644042911. The reversal of 644042900 is 9240446.

It can be written as a sum of positive squares in 3 ways, for example, as 16 + 644042884 = 4^2 + 25378^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3220115 + ... + 3220314.

Almost surely, 2^644042900 is an apocalyptic number.

It is an amenable number.

644042900 is an abundant number, since it is smaller than the sum of its proper divisors (753530410).

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

644042900 is a wasteful number, since it uses less digits than its factorization.

644042900 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6440443 (or 6440436 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 29.

The square root of 644042900 is about 25378.0003152337. Note that the first 3 decimals coincide. The cubic root of 644042900 is about 863.5846858694.

The spelling of 644042900 in words is "six hundred forty-four million, forty-two thousand, nine hundred".