644635556 has 12 divisors (see below), whose sum is σ = 1146606300. Its totient is φ = 317033760.

The previous prime is 644635501. The next prime is 644635573. The reversal of 644635556 is 655536446.

644635556 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 319193956 + 325441600 = 17866^2 + 18040^2 .

It is a hoax number, since the sum of its digits (44) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1320731 + ... + 1321218.

It is an arithmetic number, because the mean of its divisors is an integer number (95550525).

Almost surely, 2^644635556 is an apocalyptic number.

It is an amenable number.

644635556 is a deficient number, since it is larger than the sum of its proper divisors (501970744).

644635556 is a wasteful number, since it uses less digits than its factorization.

644635556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2642014 (or 2642012 counting only the distinct ones).

The product of its digits is 1296000, while the sum is 44.

The square root of 644635556 is about 25389.6742003516. The cubic root of 644635556 is about 863.8494983195.

The spelling of 644635556 in words is "six hundred forty-four million, six hundred thirty-five thousand, five hundred fifty-six".