644877939 has 4 divisors (see below), whose sum is σ = 859837256. Its totient is φ = 429918624.

The previous prime is 644877913. The next prime is 644877941. The reversal of 644877939 is 939778446.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 644877939 - 2²⁷ = 510660211 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644877539) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107479654 + ... + 107479659.

It is an arithmetic number, because the mean of its divisors is an integer number (214959314).

Almost surely, 2^644877939 is an apocalyptic number.

644877939 is a deficient number, since it is larger than the sum of its proper divisors (214959317).

644877939 is a wasteful number, since it uses less digits than its factorization.

644877939 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214959316.

The product of its digits is 9144576, while the sum is 57.

The square root of 644877939 is about 25394.4470111086. The cubic root of 644877939 is about 863.9577539036.

It can be divided in two parts, 644877 and 939, that added together give a triangular number (645816 = T₁₁₃₆).

The spelling of 644877939 in words is "six hundred forty-four million, eight hundred seventy-seven thousand, nine hundred thirty-nine".