644331653 has 32 divisors (see below), whose sum is σ = 782320896. Its totient is φ = 519187968.

The previous prime is 644331631. The next prime is 644331679. The reversal of 644331653 is 356133446.

644331653 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 644331653 - 2¹⁸ = 644069509 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644331953) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1001750 + ... + 1002392.

It is an arithmetic number, because the mean of its divisors is an integer number (24447528).

Almost surely, 2^644331653 is an apocalyptic number.

It is an amenable number.

644331653 is a deficient number, since it is larger than the sum of its proper divisors (137989243).

644331653 is a wasteful number, since it uses less digits than its factorization.

644331653 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 813.

The product of its digits is 77760, while the sum is 35.

The square root of 644331653 is about 25383.6887193331. The cubic root of 644331653 is about 863.7137276933.

The spelling of 644331653 in words is "six hundred forty-four million, three hundred thirty-one thousand, six hundred fifty-three".