644165456 has 80 divisors (see below), whose sum is σ = 1423623168. Its totient is φ = 279753600.

The previous prime is 644165443. The next prime is 644165477. The reversal of 644165456 is 654561446.

Its product of digits (345600) is a multiple of the sum of its prime factors (1920).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 354791 + ... + 356601.

Almost surely, 2^644165456 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 644165456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (711811584).

644165456 is an abundant number, since it is smaller than the sum of its proper divisors (779457712).

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

644165456 is a wasteful number, since it uses less digits than its factorization.

644165456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1920 (or 1914 counting only the distinct ones).

The product of its digits is 345600, while the sum is 41.

The square root of 644165456 is about 25380.4148114250. The cubic root of 644165456 is about 863.6394600530.

The spelling of 644165456 in words is "six hundred forty-four million, one hundred sixty-five thousand, four hundred fifty-six".