644425056 has 72 divisors (see below), whose sum is σ = 1999192104. Its totient is φ = 195279360.

The previous prime is 644425043. The next prime is 644425057. The reversal of 644425056 is 650524446.

644425056 is a `hidden beast` number, since 644 + 4 + 2 + 5 + 0 + 5 + 6 = 666.

It is a tau number, because it is divible by the number of its divisors (72).

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 644425056.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644425057) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 98541 + ... + 104876.

It is an arithmetic number, because the mean of its divisors is an integer number (27766557).

Almost surely, 2^644425056 is an apocalyptic number.

644425056 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

It is an amenable number.

644425056 is an abundant number, since it is smaller than the sum of its proper divisors (1354767048).

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

644425056 is a wasteful number, since it uses less digits than its factorization.

644425056 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 203444 (or 203433 counting only the distinct ones).

The product of its (nonzero) digits is 115200, while the sum is 36.

The square root of 644425056 is about 25385.5284758856. The cubic root of 644425056 is about 863.7554606295.

The spelling of 644425056 in words is "six hundred forty-four million, four hundred twenty-five thousand, fifty-six".