644371097656 has 32 divisors (see below), whose sum is σ = 1419418854000. Its totient is φ = 270365495040.

The previous prime is 644371097647. The next prime is 644371097659. The reversal of 644371097656 is 656790173446.

It is a super-2 number, since 2×644371097656² (a number of 24 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 644371097656.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644371097659) 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, 281629581 + ... + 281631868.

Almost surely, 2^644371097656 is an apocalyptic number.

It is an amenable number.

644371097656 is an abundant number, since it is smaller than the sum of its proper divisors (775047756344).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644371097656 is a wasteful number, since it uses less digits than its factorization.

644371097656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 563261479 (or 563261475 counting only the distinct ones).

The product of its (nonzero) digits is 22861440, while the sum is 58.

The spelling of 644371097656 in words is "six hundred forty-four billion, three hundred seventy-one million, ninety-seven thousand, six hundred fifty-six".