644539631 has 8 divisors (see below), whose sum is σ = 666059904. Its totient is φ = 623064960.

The previous prime is 644539607. The next prime is 644539663. The reversal of 644539631 is 136935446.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 644539631 - 2¹⁰ = 644538607 is a prime.

It is a super-2 number, since 2×644539631² = 830862671859232322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644539331) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18635 + ... + 40451.

It is an arithmetic number, because the mean of its divisors is an integer number (83257488).

Almost surely, 2^644539631 is an apocalyptic number.

644539631 is a deficient number, since it is larger than the sum of its proper divisors (21520273).

644539631 is a wasteful number, since it uses less digits than its factorization.

644539631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22801.

The product of its digits is 233280, while the sum is 41.

The square root of 644539631 is about 25387.7850747165. The cubic root of 644539631 is about 863.8066478164.

The spelling of 644539631 in words is "six hundred forty-four million, five hundred thirty-nine thousand, six hundred thirty-one".