644315913 has 24 divisors (see below), whose sum is σ = 953903808. Its totient is φ = 418858272.

The previous prime is 644315909. The next prime is 644315927. The reversal of 644315913 is 319513446.

644315913 is a `hidden beast` number, since 64 + 4 + 3 + 1 + 591 + 3 = 666.

It is not a de Polignac number, because 644315913 - 2² = 644315909 is a prime.

It is not an unprimeable number, because it can be changed into a prime (644315953) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 342331 + ... + 344207.

It is an arithmetic number, because the mean of its divisors is an integer number (39745992).

Almost surely, 2^644315913 is an apocalyptic number.

It is an amenable number.

644315913 is a deficient number, since it is larger than the sum of its proper divisors (309587895).

644315913 is a wasteful number, since it uses less digits than its factorization.

644315913 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2813 (or 2810 counting only the distinct ones).

The product of its digits is 38880, while the sum is 36.

The square root of 644315913 is about 25383.3786758186. The cubic root of 644315913 is about 863.7066945840.

The spelling of 644315913 in words is "six hundred forty-four million, three hundred fifteen thousand, nine hundred thirteen".