638891856 has 30 divisors (see below), whose sum is σ = 1788010250. Its totient is φ = 212963904.

The previous prime is 638891849. The next prime is 638891879. The reversal of 638891856 is 658198836.

It can be written as a sum of positive squares in only one way, i.e., 482241600 + 156650256 = 21960^2 + 12516^2 .

It is a congruent number.

It is an unprimeable number.

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, 2218231 + ... + 2218518.

Almost surely, 2^638891856 is an apocalyptic number.

It is an amenable number.

638891856 is an abundant number, since it is smaller than the sum of its proper divisors (1149118394).

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

638891856 is a wasteful number, since it uses less digits than its factorization.

638891856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4436763 (or 4436754 counting only the distinct ones).

The product of its digits is 2488320, while the sum is 54.

The square root of 638891856 is about 25276.3101737576. The cubic root of 638891856 is about 861.2762086953.

The spelling of 638891856 in words is "six hundred thirty-eight million, eight hundred ninety-one thousand, eight hundred fifty-six".