644439931 has 4 divisors (see below), whose sum is σ = 647779192. Its totient is φ = 641100672.

The previous prime is 644439923. The next prime is 644439973. The reversal of 644439931 is 139934446.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 644439931 - 2³ = 644439923 is a prime.

It is a super-2 number, since 2×644439931² = 830605649334569522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644439911) 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 3 ways as a sum of consecutive naturals, for example, 1669341 + ... + 1669726.

It is an arithmetic number, because the mean of its divisors is an integer number (161944798).

Almost surely, 2^644439931 is an apocalyptic number.

644439931 is a deficient number, since it is larger than the sum of its proper divisors (3339261).

644439931 is a wasteful number, since it uses less digits than its factorization.

644439931 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3339260.

The product of its digits is 279936, while the sum is 43.

The square root of 644439931 is about 25385.8214560806. The cubic root of 644439931 is about 863.7621064831.

The spelling of 644439931 in words is "six hundred forty-four million, four hundred thirty-nine thousand, nine hundred thirty-one".