644353660 has 24 divisors (see below), whose sum is σ = 1360161936. Its totient is φ = 256404480.

The previous prime is 644353657. The next prime is 644353727. The reversal of 644353660 is 66353446.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 79606 + ... + 87325.

It is an arithmetic number, because the mean of its divisors is an integer number (56673414).

Almost surely, 2^644353660 is an apocalyptic number.

It is an amenable number.

644353660 is an abundant number, since it is smaller than the sum of its proper divisors (715808276).

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

644353660 is a wasteful number, since it uses less digits than its factorization.

644353660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 167133 (or 167131 counting only the distinct ones).

The product of its (nonzero) digits is 155520, while the sum is 37.

The square root of 644353660 is about 25384.1222026683. The cubic root of 644353660 is about 863.7235608961.

The spelling of 644353660 in words is "six hundred forty-four million, three hundred fifty-three thousand, six hundred sixty".