644620944 has 80 divisors (see below), whose sum is σ = 1875308544. Its totient is φ = 189033600.

The previous prime is 644620939. The next prime is 644620967. The reversal of 644620944 is 449026446.

It is a super-2 number, since 2×644620944² = 831072322886902272, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3324 + ... + 36059.

Almost surely, 2^644620944 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 644620944, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (937654272).

644620944 is an abundant number, since it is smaller than the sum of its proper divisors (1230687600).

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

644620944 is a wasteful number, since it uses less digits than its factorization.

644620944 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39436 (or 39430 counting only the distinct ones).

The product of its (nonzero) digits is 165888, while the sum is 39.

The square root of 644620944 is about 25389.3864439454. The cubic root of 644620944 is about 863.8429712909.

The spelling of 644620944 in words is "six hundred forty-four million, six hundred twenty thousand, nine hundred forty-four".