644420631 has 16 divisors (see below), whose sum is σ = 865317600. Its totient is φ = 426577920.

The previous prime is 644420603. The next prime is 644420639. The reversal of 644420631 is 136024446.

It is not a de Polignac number, because 644420631 - 2¹¹ = 644418583 is a prime.

It is a super-2 number, since 2×644420631² = 830555899316876322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644420639) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 606841 + ... + 607901.

It is an arithmetic number, because the mean of its divisors is an integer number (54082350).

Almost surely, 2^644420631 is an apocalyptic number.

644420631 is a deficient number, since it is larger than the sum of its proper divisors (220896969).

644420631 is a wasteful number, since it uses less digits than its factorization.

644420631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2306.

The product of its (nonzero) digits is 13824, while the sum is 30.

The square root of 644420631 is about 25385.4413197801. The cubic root of 644420631 is about 863.7534836080.

The spelling of 644420631 in words is "six hundred forty-four million, four hundred twenty thousand, six hundred thirty-one".