644040264863 has 16 divisors (see below), whose sum is σ = 665048494656. Its totient is φ = 623302901760.

The previous prime is 644040264839. The next prime is 644040264911. The reversal of 644040264863 is 368462040446.

It is a cyclic number.

It is not a de Polignac number, because 644040264863 - 2¹² = 644040260767 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644040260863) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2678006 + ... + 2908572.

It is an arithmetic number, because the mean of its divisors is an integer number (41565530916).

Almost surely, 2^644040264863 is an apocalyptic number.

644040264863 is a deficient number, since it is larger than the sum of its proper divisors (21008229793).

644040264863 is a wasteful number, since it uses less digits than its factorization.

644040264863 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 231154.

The product of its (nonzero) digits is 2654208, while the sum is 47.

The spelling of 644040264863 in words is "six hundred forty-four billion, forty million, two hundred sixty-four thousand, eight hundred sixty-three".