644885875 has 16 divisors (see below), whose sum is σ = 808194816. Its totient is φ = 513744000.

The previous prime is 644885863. The next prime is 644885881. The reversal of 644885875 is 578588446.

644885875 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 644885875 - 2¹⁵ = 644853107 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19422 + ... + 40828.

It is an arithmetic number, because the mean of its divisors is an integer number (50512176).

Almost surely, 2^644885875 is an apocalyptic number.

644885875 is a deficient number, since it is larger than the sum of its proper divisors (163308941).

644885875 is a wasteful number, since it uses less digits than its factorization.

644885875 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21663 (or 21653 counting only the distinct ones).

The product of its digits is 8601600, while the sum is 55.

The square root of 644885875 is about 25394.6032652609. The cubic root of 644885875 is about 863.9612979027.

The spelling of 644885875 in words is "six hundred forty-four million, eight hundred eighty-five thousand, eight hundred seventy-five".