644452731 has 12 divisors (see below), whose sum is σ = 1002482208. Its totient is φ = 396586224.

The previous prime is 644452727. The next prime is 644452733. The reversal of 644452731 is 137254446.

644452731 is a `hidden beast` number, since 64 + 44 + 527 + 31 = 666.

It is not a de Polignac number, because 644452731 - 2² = 644452727 is a prime.

It is a super-2 number, since 2×644452731² = 830638644986716722, which contains 22 as substring.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (644452733) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2753955 + ... + 2754188.

It is an arithmetic number, because the mean of its divisors is an integer number (83540184).

Almost surely, 2^644452731 is an apocalyptic number.

644452731 is a deficient number, since it is larger than the sum of its proper divisors (358029477).

644452731 is a wasteful number, since it uses less digits than its factorization.

644452731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5508162 (or 5508159 counting only the distinct ones).

The product of its digits is 80640, while the sum is 36.

The square root of 644452731 is about 25386.0735640626. The cubic root of 644452731 is about 863.7678251861.

It can be divided in two parts, 64445 and 2731, that added together give a palindrome (67176).

The spelling of 644452731 in words is "six hundred forty-four million, four hundred fifty-two thousand, seven hundred thirty-one".