644440745108 has 48 divisors (see below), whose sum is σ = 1203223467600. Its totient is φ = 302005647360.

The previous prime is 644440745099. The next prime is 644440745147. The reversal of 644440745108 is 801547044446.

It can be written as a sum of positive squares in 8 ways, for example, as 15652011664 + 628788733444 = 125108^2 + 792962^2 .

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, 4668098 + ... + 4804166.

It is an arithmetic number, because the mean of its divisors is an integer number (25067155575).

Almost surely, 2^644440745108 is an apocalyptic number.

644440745108 is a gapful number since it is divisible by the number (68) formed by its first and last digit.

It is an amenable number.

644440745108 is a deficient number, since it is larger than the sum of its proper divisors (558782722492).

644440745108 is a wasteful number, since it uses less digits than its factorization.

644440745108 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 136365 (or 136329 counting only the distinct ones).

The product of its (nonzero) digits is 1720320, while the sum is 47.

The spelling of 644440745108 in words is "six hundred forty-four billion, four hundred forty million, seven hundred forty-five thousand, one hundred eight".