644539330688 has 72 divisors (see below), whose sum is σ = 1411605144495. Its totient is φ = 292927008000.

The previous prime is 644539330667. The next prime is 644539330693. The reversal of 644539330688 is 886033935446.

It is a happy number.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It can be written as a sum of positive squares in only one way, i.e., 322269665344 + 322269665344 = 567688^2 + 567688^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=567688.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 99909863 + ... + 99916313.

Almost surely, 2^644539330688 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644539330688

644539330688 is an abundant number, since it is smaller than the sum of its proper divisors (767065813807).

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

644539330688 is an frugal number, since it uses more digits than its factorization.

644539330688 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12938 (or 6464 counting only the distinct ones).

The product of its (nonzero) digits is 44789760, while the sum is 59.

The spelling of 644539330688 in words is "six hundred forty-four billion, five hundred thirty-nine million, three hundred thirty thousand, six hundred eighty-eight".