644260664 has 32 divisors (see below), whose sum is σ = 1273314000. Its totient is φ = 304756992.

The previous prime is 644260663. The next prime is 644260703. The reversal of 644260664 is 466062446.

It is a Harshad number since it is a multiple of its sum of digits (38).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644260663) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 127172 + ... + 132140.

Almost surely, 2^644260664 is an apocalyptic number.

It is an amenable number.

644260664 is a deficient number, since it is larger than the sum of its proper divisors (629053336).

644260664 is a wasteful number, since it uses less digits than its factorization.

644260664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5847 (or 5843 counting only the distinct ones).

The product of its (nonzero) digits is 165888, while the sum is 38.

The square root of 644260664 is about 25382.2903615887. The cubic root of 644260664 is about 863.6820067488.

The spelling of 644260664 in words is "six hundred forty-four million, two hundred sixty thousand, six hundred sixty-four".