644655672 has 48 divisors (see below), whose sum is σ = 1810612440. Its totient is φ = 214884576.

The previous prime is 644655667. The next prime is 644655677. The reversal of 644655672 is 276556446.

It is an interprime number because it is at equal distance from previous prime (644655667) and next prime (644655677).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644655677) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 163863 + ... + 167750.

Almost surely, 2^644655672 is an apocalyptic number.

It is an amenable number.

644655672 is an abundant number, since it is smaller than the sum of its proper divisors (1165956768).

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

644655672 is a wasteful number, since it uses less digits than its factorization.

644655672 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 331634 (or 331618 counting only the distinct ones).

The product of its digits is 1209600, while the sum is 45.

The square root of 644655672 is about 25390.0703425571. The cubic root of 644655672 is about 863.8584837665.

The spelling of 644655672 in words is "six hundred forty-four million, six hundred fifty-five thousand, six hundred seventy-two".