644365231 has 4 divisors (see below), whose sum is σ = 646277632. Its totient is φ = 642452832.

The previous prime is 644365223. The next prime is 644365291. The reversal of 644365231 is 132563446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 132563446 = 2 ⋅66281723.

It is a cyclic number.

It is not a de Polignac number, because 644365231 - 2³ = 644365223 is a prime.

It is a super-2 number, since 2×644365231² = 830413101843366722, 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 (644365201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 955695 + ... + 956368.

It is an arithmetic number, because the mean of its divisors is an integer number (161569408).

Almost surely, 2^644365231 is an apocalyptic number.

644365231 is a deficient number, since it is larger than the sum of its proper divisors (1912401).

644365231 is a wasteful number, since it uses less digits than its factorization.

644365231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1912400.

The product of its digits is 51840, while the sum is 34.

The square root of 644365231 is about 25384.3501197096. The cubic root of 644365231 is about 863.7287309790.

The spelling of 644365231 in words is "six hundred forty-four million, three hundred sixty-five thousand, two hundred thirty-one".