644863838 has 16 divisors (see below), whose sum is σ = 1027554000. Its totient is φ = 302657472.

The previous prime is 644863783. The next prime is 644863859. The reversal of 644863838 is 838368446.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 73703 + ... + 81986.

It is an arithmetic number, because the mean of its divisors is an integer number (64222125).

Almost surely, 2^644863838 is an apocalyptic number.

644863838 is a deficient number, since it is larger than the sum of its proper divisors (382690162).

644863838 is a wasteful number, since it uses less digits than its factorization.

644863838 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 155819.

The product of its digits is 2654208, while the sum is 50.

The square root of 644863838 is about 25394.1693701527. The cubic root of 644863838 is about 863.9514567134.

The spelling of 644863838 in words is "six hundred forty-four million, eight hundred sixty-three thousand, eight hundred thirty-eight".