644117838521 has 8 divisors (see below), whose sum is σ = 687823276800. Its totient is φ = 601845365520.

The previous prime is 644117838509. The next prime is 644117838563. The reversal of 644117838521 is 125838711446.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 644117838521 - 2⁶ = 644117838457 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644117838521.

It is not an unprimeable number, because it can be changed into a prime (644117832521) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 358240391 + ... + 358242188.

It is an arithmetic number, because the mean of its divisors is an integer number (85977909600).

Almost surely, 2^644117838521 is an apocalyptic number.

It is an amenable number.

644117838521 is a deficient number, since it is larger than the sum of its proper divisors (43705438279).

644117838521 is a wasteful number, since it uses less digits than its factorization.

644117838521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 716482639.

The product of its digits is 1290240, while the sum is 50.

The spelling of 644117838521 in words is "six hundred forty-four billion, one hundred seventeen million, eight hundred thirty-eight thousand, five hundred twenty-one".