644355938561 has 8 divisors (see below), whose sum is σ = 659568212160. Its totient is φ = 629153994672.

The previous prime is 644355938557. The next prime is 644355938591. The reversal of 644355938561 is 165839553446.

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 644355938561 - 2² = 644355938557 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 644355938561.

It is not an unprimeable number, because it can be changed into a prime (644355938591) 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, 2456126 + ... + 2705783.

It is an arithmetic number, because the mean of its divisors is an integer number (82446026520).

Almost surely, 2^644355938561 is an apocalyptic number.

It is an amenable number.

644355938561 is a deficient number, since it is larger than the sum of its proper divisors (15212273599).

644355938561 is a wasteful number, since it uses less digits than its factorization.

644355938561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5164855.

The product of its digits is 46656000, while the sum is 59.

The spelling of 644355938561 in words is "six hundred forty-four billion, three hundred fifty-five million, nine hundred thirty-eight thousand, five hundred sixty-one".