644257633 has 4 divisors (see below), whose sum is σ = 648892720. Its totient is φ = 639622548.

The previous prime is 644257609. The next prime is 644257637. The reversal of 644257633 is 336752446.

644257633 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644257633 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644257637) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2317335 + ... + 2317612.

It is an arithmetic number, because the mean of its divisors is an integer number (162223180).

Almost surely, 2^644257633 is an apocalyptic number.

It is an amenable number.

644257633 is a deficient number, since it is larger than the sum of its proper divisors (4635087).

644257633 is a wasteful number, since it uses less digits than its factorization.

644257633 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4635086.

The product of its digits is 362880, while the sum is 40.

The square root of 644257633 is about 25382.2306545347. The cubic root of 644257633 is about 863.6806523155.

The spelling of 644257633 in words is "six hundred forty-four million, two hundred fifty-seven thousand, six hundred thirty-three".