644868279 has 24 divisors (see below), whose sum is σ = 1027587600. Its totient is φ = 386432640.

The previous prime is 644868277. The next prime is 644868283. The reversal of 644868279 is 972868446.

It is not a de Polignac number, because 644868279 - 2¹ = 644868277 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644868277) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 27784 + ... + 45405.

It is an arithmetic number, because the mean of its divisors is an integer number (42816150).

Almost surely, 2^644868279 is an apocalyptic number.

644868279 is a deficient number, since it is larger than the sum of its proper divisors (382719321).

644868279 is a wasteful number, since it uses less digits than its factorization.

644868279 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73295 (or 73292 counting only the distinct ones).

The product of its digits is 4644864, while the sum is 54.

The square root of 644868279 is about 25394.2568113343. The cubic root of 644868279 is about 863.9534399743.

The spelling of 644868279 in words is "six hundred forty-four million, eight hundred sixty-eight thousand, two hundred seventy-nine".