644247612 has 72 divisors (see below), whose sum is σ = 1688284416. Its totient is φ = 207006624.

The previous prime is 644247601. The next prime is 644247647. The reversal of 644247612 is 216742446.

644247612 is a `hidden beast` number, since 644 + 2 + 4 + 7 + 6 + 1 + 2 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 110523 + ... + 116205.

Almost surely, 2^644247612 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644247612, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (844142208).

644247612 is an abundant number, since it is smaller than the sum of its proper divisors (1044036804).

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

644247612 is a wasteful number, since it uses less digits than its factorization.

644247612 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5807 (or 5802 counting only the distinct ones).

The product of its digits is 64512, while the sum is 36.

The square root of 644247612 is about 25382.0332518890. The cubic root of 644247612 is about 863.6761742991.

The spelling of 644247612 in words is "six hundred forty-four million, two hundred forty-seven thousand, six hundred twelve".