644920365 has 32 divisors (see below), whose sum is σ = 1074431232. Its totient is φ = 330048000.

The previous prime is 644920349. The next prime is 644920387. The reversal of 644920365 is 563029446.

It is not a de Polignac number, because 644920365 - 2⁴ = 644920349 is a prime.

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 28920 + ... + 46110.

It is an arithmetic number, because the mean of its divisors is an integer number (33575976).

Almost surely, 2^644920365 is an apocalyptic number.

It is an amenable number.

644920365 is a deficient number, since it is larger than the sum of its proper divisors (429510867).

644920365 is a wasteful number, since it uses less digits than its factorization.

644920365 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17301.

The product of its (nonzero) digits is 155520, while the sum is 39.

The square root of 644920365 is about 25395.2823374736. The cubic root of 644920365 is about 863.9766998496.

The spelling of 644920365 in words is "six hundred forty-four million, nine hundred twenty thousand, three hundred sixty-five".