644023263 has 32 divisors (see below), whose sum is σ = 940294656. Its totient is φ = 389720448.

The previous prime is 644023249. The next prime is 644023283. The reversal of 644023263 is 362320446.

It is a happy number.

It is not a de Polignac number, because 644023263 - 2⁶ = 644023199 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 644023263.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644023283) 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, 654670 + ... + 655652.

It is an arithmetic number, because the mean of its divisors is an integer number (29384208).

Almost surely, 2^644023263 is an apocalyptic number.

644023263 is a deficient number, since it is larger than the sum of its proper divisors (296271393).

644023263 is a wasteful number, since it uses less digits than its factorization.

644023263 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1263.

The product of its (nonzero) digits is 20736, while the sum is 30.

The square root of 644023263 is about 25377.6134220695. The cubic root of 644023263 is about 863.5759088222.

The spelling of 644023263 in words is "six hundred forty-four million, twenty-three thousand, two hundred sixty-three".