644902048720 has 80 divisors (see below), whose sum is σ = 1572348983760. Its totient is φ = 245653696512.

The previous prime is 644902048643. The next prime is 644902048759. The reversal of 644902048720 is 27840209446.

It can be written as a sum of positive squares in 8 ways, for example, as 21926501776 + 622975546944 = 148076^2 + 789288^2 .

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1734579 + ... + 2073298.

It is an arithmetic number, because the mean of its divisors is an integer number (19654362297).

Almost surely, 2^644902048720 is an apocalyptic number.

It is an amenable number.

644902048720 is an abundant number, since it is smaller than the sum of its proper divisors (927446935040).

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

644902048720 is a wasteful number, since it uses less digits than its factorization.

644902048720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3807992 (or 3807986 counting only the distinct ones).

The product of its (nonzero) digits is 774144, while the sum is 46.

The spelling of 644902048720 in words is "six hundred forty-four billion, nine hundred two million, forty-eight thousand, seven hundred twenty".