644877988 has 12 divisors (see below), whose sum is σ = 1167451740. Its totient is φ = 311320352.

The previous prime is 644877967. The next prime is 644877991. The reversal of 644877988 is 889778446.

It can be written as a sum of positive squares in 2 ways, for example, as 543915684 + 100962304 = 23322^2 + 10048^2 .

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, 2779531 + ... + 2779762.

It is an arithmetic number, because the mean of its divisors is an integer number (97287645).

Almost surely, 2^644877988 is an apocalyptic number.

It is an amenable number.

644877988 is a deficient number, since it is larger than the sum of its proper divisors (522573752).

644877988 is a wasteful number, since it uses less digits than its factorization.

644877988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5559326 (or 5559324 counting only the distinct ones).

The product of its digits is 21676032, while the sum is 61.

The square root of 644877988 is about 25394.4479758864. The cubic root of 644877988 is about 863.9577757857.

The spelling of 644877988 in words is "six hundred forty-four million, eight hundred seventy-seven thousand, nine hundred eighty-eight".