644431131 has 12 divisors (see below), whose sum is σ = 960872640. Its totient is φ = 415761840.

The previous prime is 644431129. The next prime is 644431141. The reversal of 644431131 is 131134446.

644431131 is a `hidden beast` number, since 644 + 4 + 3 + 1 + 13 + 1 = 666.

It is not a de Polignac number, because 644431131 - 2¹ = 644431129 is a prime.

It is a super-2 number, since 2×644431131² = 830582965203878322, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 644431095 and 644431104.

It is not an unprimeable number, because it can be changed into a prime (644431141) 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, 1154616 + ... + 1155173.

It is an arithmetic number, because the mean of its divisors is an integer number (80072720).

Almost surely, 2^644431131 is an apocalyptic number.

644431131 is a deficient number, since it is larger than the sum of its proper divisors (316441509).

644431131 is a wasteful number, since it uses less digits than its factorization.

644431131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2309826 (or 2309823 counting only the distinct ones).

The product of its digits is 3456, while the sum is 27.

The square root of 644431131 is about 25385.6481303905. The cubic root of 644431131 is about 863.7581748308.

Adding to 644431131 its reverse (131134446), we get a palindrome (775565577).

The spelling of 644431131 in words is "six hundred forty-four million, four hundred thirty-one thousand, one hundred thirty-one".