644840568 has 32 divisors (see below), whose sum is σ = 1791224400. Its totient is φ = 214946784.

The previous prime is 644840543. The next prime is 644840569. The reversal of 644840568 is 865048446.

644840568 is a `hidden beast` number, since 6 + 4 + 4 + 84 + 0 + 568 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644840569) 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, 1492471 + ... + 1492902.

Almost surely, 2^644840568 is an apocalyptic number.

It is an amenable number.

644840568 is an abundant number, since it is smaller than the sum of its proper divisors (1146383832).

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

644840568 is a wasteful number, since it uses less digits than its factorization.

644840568 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2985388 (or 2985378 counting only the distinct ones).

The product of its (nonzero) digits is 737280, while the sum is 45.

The square root of 644840568 is about 25393.7111899777. The cubic root of 644840568 is about 863.9410646528.

The spelling of 644840568 in words is "six hundred forty-four million, eight hundred forty thousand, five hundred sixty-eight".