644291568 has 60 divisors (see below), whose sum is σ = 1909194768. Its totient is φ = 202129920.

The previous prime is 644291537. The next prime is 644291573. The reversal of 644291568 is 865192446.

644291568 is a `hidden beast` number, since 64 + 4 + 29 + 1 + 568 = 666.

It is a super-2 number, since 2×644291568² = 830223249191797248, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 129148 + ... + 134043.

Almost surely, 2^644291568 is an apocalyptic number.

644291568 is a gapful number since it is divisible by the number (68) formed by its first and last digit.

It is an amenable number.

644291568 is an abundant number, since it is smaller than the sum of its proper divisors (1264903200).

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

644291568 is a wasteful number, since it uses less digits than its factorization.

644291568 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 263222 (or 263213 counting only the distinct ones).

The product of its digits is 414720, while the sum is 45.

The square root of 644291568 is about 25382.8991251984. The cubic root of 644291568 is about 863.6958162742.

The spelling of 644291568 in words is "six hundred forty-four million, two hundred ninety-one thousand, five hundred sixty-eight".