644737456 has 40 divisors (see below), whose sum is σ = 1371479184. Its totient is φ = 291183360.

The previous prime is 644737447. The next prime is 644737517. The reversal of 644737456 is 654737446.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15966 + ... + 39298.

Almost surely, 2^644737456 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 644737456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (685739592).

644737456 is an abundant number, since it is smaller than the sum of its proper divisors (726741728).

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

644737456 is a wasteful number, since it uses less digits than its factorization.

644737456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23509 (or 23503 counting only the distinct ones).

The product of its digits is 1693440, while the sum is 46.

The square root of 644737456 is about 25391.6808423546. The cubic root of 644737456 is about 863.8950132493.

The spelling of 644737456 in words is "six hundred forty-four million, seven hundred thirty-seven thousand, four hundred fifty-six".