644973879 has 16 divisors (see below), whose sum is σ = 968408064. Its totient is φ = 378283200.

The previous prime is 644973877. The next prime is 644973887. The reversal of 644973879 is 978379446.

644973879 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 644973879 - 2¹ = 644973877 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644973877) 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, 314214 + ... + 316259.

It is an arithmetic number, because the mean of its divisors is an integer number (60525504).

Almost surely, 2^644973879 is an apocalyptic number.

644973879 is a deficient number, since it is larger than the sum of its proper divisors (323434185).

644973879 is a wasteful number, since it uses less digits than its factorization.

644973879 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 630518.

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

The square root of 644973879 is about 25396.3359365086. The cubic root of 644973879 is about 864.0005961180. Note that the first 3 decimals are identical.

The spelling of 644973879 in words is "six hundred forty-four million, nine hundred seventy-three thousand, eight hundred seventy-nine".