644775650 has 12 divisors (see below), whose sum is σ = 1199282802. Its totient is φ = 257910240.

The previous prime is 644775631. The next prime is 644775667. The reversal of 644775650 is 56577446.

It can be written as a sum of positive squares in 3 ways, for example, as 345104929 + 299670721 = 18577^2 + 17311^2 .

It is a Curzon 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, 6447707 + ... + 6447806.

Almost surely, 2^644775650 is an apocalyptic number.

644775650 is a deficient number, since it is larger than the sum of its proper divisors (554507152).

644775650 is a wasteful number, since it uses less digits than its factorization.

644775650 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12895525 (or 12895520 counting only the distinct ones).

The product of its (nonzero) digits is 705600, while the sum is 44.

The square root of 644775650 is about 25392.4329279413. The cubic root of 644775650 is about 863.9120718490.

The spelling of 644775650 in words is "six hundred forty-four million, seven hundred seventy-five thousand, six hundred fifty".