644845506768 has 30 divisors (see below), whose sum is σ = 1804671800594. Its totient is φ = 214948502208.

The previous prime is 644845506737. The next prime is 644845506787. The reversal of 644845506768 is 867605548446.

It is a happy number.

644845506768 is a `hidden beast` number, since 6 + 4 + 4 + 8 + 4 + 550 + 6 + 76 + 8 = 666.

It can be written as a sum of positive squares in only one way, i.e., 620175150144 + 24670356624 = 787512^2 + 157068^2 .

It is a hoax number, since the sum of its digits (63) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 2239046755 + ... + 2239047042.

Almost surely, 2^644845506768 is an apocalyptic number.

It is an amenable number.

644845506768 is an abundant number, since it is smaller than the sum of its proper divisors (1159826293826).

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

644845506768 is a wasteful number, since it uses less digits than its factorization.

644845506768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4478093811 (or 4478093802 counting only the distinct ones).

The product of its (nonzero) digits is 154828800, while the sum is 63.

The spelling of 644845506768 in words is "six hundred forty-four billion, eight hundred forty-five million, five hundred six thousand, seven hundred sixty-eight".