644217564 has 24 divisors (see below), whose sum is σ = 1509921280. Its totient is φ = 213775344.

The previous prime is 644217559. The next prime is 644217631. The reversal of 644217564 is 465712446.

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors.

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, 117694 + ... + 123045.

Almost surely, 2^644217564 is an apocalyptic number.

It is an amenable number.

644217564 is an abundant number, since it is smaller than the sum of its proper divisors (865703716).

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

644217564 is a wasteful number, since it uses less digits than its factorization.

644217564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 240969 (or 240967 counting only the distinct ones).

The product of its digits is 161280, while the sum is 39.

The square root of 644217564 is about 25381.4413302318. The cubic root of 644217564 is about 863.6627466746.

The spelling of 644217564 in words is "six hundred forty-four million, two hundred seventeen thousand, five hundred sixty-four".