644243650 has 48 divisors (see below), whose sum is σ = 1218268008. Its totient is φ = 253440000.

The previous prime is 644243647. The next prime is 644243669. The reversal of 644243650 is 56342446.

It can be written as a sum of positive squares in 12 ways, for example, as 185041609 + 459202041 = 13603^2 + 21429^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 974320 + ... + 974980.

Almost surely, 2^644243650 is an apocalyptic number.

644243650 is a deficient number, since it is larger than the sum of its proper divisors (574024358).

644243650 is a wasteful number, since it uses less digits than its factorization.

644243650 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 967 (or 962 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 34.

The square root of 644243650 is about 25381.9552044361. The cubic root of 644243650 is about 863.6744038142.

The spelling of 644243650 in words is "six hundred forty-four million, two hundred forty-three thousand, six hundred fifty".