644668144 has 20 divisors (see below), whose sum is σ = 1292115960. Its totient is φ = 311218880.

The previous prime is 644668139. The next prime is 644668151. The reversal of 644668144 is 441866446.

It is a self number, because there is not a number n which added to its sum of digits gives 644668144.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 694222 + ... + 695149.

It is an arithmetic number, because the mean of its divisors is an integer number (64605798).

Almost surely, 2^644668144 is an apocalyptic number.

It is an amenable number.

644668144 is an abundant number, since it is smaller than the sum of its proper divisors (647447816).

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

644668144 is a wasteful number, since it uses less digits than its factorization.

644668144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1389408 (or 1389402 counting only the distinct ones).

The product of its digits is 442368, while the sum is 43.

The square root of 644668144 is about 25390.3159491961. The cubic root of 644668144 is about 863.8640546855.

The spelling of 644668144 in words is "six hundred forty-four million, six hundred sixty-eight thousand, one hundred forty-four".