644864868 has 48 divisors (see below), whose sum is σ = 1673703360. Its totient is φ = 214719552.

The previous prime is 644864861. The next prime is 644864881. The reversal of 644864868 is 868468446.

644864868 is a `hidden beast` number, since 64 + 486 + 48 + 68 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is not an unprimeable number, because it can be changed into a prime (644864861) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 115755 + ... + 121197.

It is an arithmetic number, because the mean of its divisors is an integer number (34868820).

Almost surely, 2^644864868 is an apocalyptic number.

It is an amenable number.

644864868 is an abundant number, since it is smaller than the sum of its proper divisors (1028838492).

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

644864868 is a wasteful number, since it uses less digits than its factorization.

644864868 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6553 (or 6545 counting only the distinct ones).

The product of its digits is 7077888, while the sum is 54.

The square root of 644864868 is about 25394.1896503905. The cubic root of 644864868 is about 863.9519166914.

The spelling of 644864868 in words is "six hundred forty-four million, eight hundred sixty-four thousand, eight hundred sixty-eight".