644835872 has 30 divisors (see below), whose sum is σ = 1288755783. Its totient is φ = 317605728.

The previous prime is 644835859. The next prime is 644835899. The reversal of 644835872 is 278538446.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It can be written as a sum of positive squares in only one way, i.e., 322417936 + 322417936 = 17956^2 + 17956^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=17956.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 4 ways as a sum of consecutive naturals, for example, 9624383 + ... + 9624449.

Almost surely, 2^644835872 is an apocalyptic number.

It is an amenable number.

644835872 is a deficient number, since it is larger than the sum of its proper divisors (643919911).

644835872 is an frugal number, since it uses more digits than its factorization.

644835872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 278 (or 69 counting only the distinct ones).

The product of its digits is 1290240, while the sum is 47.

The square root of 644835872 is about 25393.6187259713. The cubic root of 644835872 is about 863.9389674538.

The spelling of 644835872 in words is "six hundred forty-four million, eight hundred thirty-five thousand, eight hundred seventy-two".