644036256 has 36 divisors (see below), whose sum is σ = 1831478922. Its totient is φ = 214678656.

The previous prime is 644036249. The next prime is 644036257. The reversal of 644036256 is 652630446.

644036256 is a `hidden beast` number, since 644 + 0 + 3 + 6 + 2 + 5 + 6 = 666.

It can be written as a sum of positive squares in only one way, i.e., 543635856 + 100400400 = 23316^2 + 10020^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 644036256.

It is not an unprimeable number, because it can be changed into a prime (644036257) by changing a digit.

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 5 ways as a sum of consecutive naturals, for example, 1117831 + ... + 1118406.

Almost surely, 2^644036256 is an apocalyptic number.

It is an amenable number.

644036256 is an abundant number, since it is smaller than the sum of its proper divisors (1187442666).

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

644036256 is a wasteful number, since it uses less digits than its factorization.

644036256 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2236253 (or 2236242 counting only the distinct ones).

The product of its (nonzero) digits is 103680, while the sum is 36.

The square root of 644036256 is about 25377.8694141175. The cubic root of 644036256 is about 863.5817162555.

The spelling of 644036256 in words is "six hundred forty-four million, thirty-six thousand, two hundred fifty-six".