644733644 has 12 divisors (see below), whose sum is σ = 1146780768. Its totient is φ = 317082000.

The previous prime is 644733643. The next prime is 644733667. The reversal of 644733644 is 446337446.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (644733641) 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, 1320932 + ... + 1321419.

It is an arithmetic number, because the mean of its divisors is an integer number (95565064).

Almost surely, 2^644733644 is an apocalyptic number.

It is an amenable number.

644733644 is a deficient number, since it is larger than the sum of its proper divisors (502047124).

644733644 is a wasteful number, since it uses less digits than its factorization.

644733644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2642416 (or 2642414 counting only the distinct ones).

The product of its digits is 580608, while the sum is 41.

The square root of 644733644 is about 25391.6057782882. The cubic root of 644733644 is about 863.8933106574.

The spelling of 644733644 in words is "six hundred forty-four million, seven hundred thirty-three thousand, six hundred forty-four".