644861393 has 12 divisors (see below), whose sum is σ = 709492224. Its totient is φ = 585677400.

The previous prime is 644861383. The next prime is 644861401. The reversal of 644861393 is 393168446.

It is not a de Polignac number, because 644861393 - 2⁸ = 644861137 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644861303) 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, 176180 + ... + 179802.

It is an arithmetic number, because the mean of its divisors is an integer number (59124352).

Almost surely, 2^644861393 is an apocalyptic number.

It is an amenable number.

644861393 is a deficient number, since it is larger than the sum of its proper divisors (64630831).

644861393 is a wasteful number, since it uses less digits than its factorization.

644861393 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5116 (or 5105 counting only the distinct ones).

The product of its digits is 373248, while the sum is 44.

The square root of 644861393 is about 25394.1212291349. The cubic root of 644861393 is about 863.9503648219.

The spelling of 644861393 in words is "six hundred forty-four million, eight hundred sixty-one thousand, three hundred ninety-three".