638666836 has 48 divisors (see below), whose sum is σ = 1219778560. Its totient is φ = 291483360.

The previous prime is 638666803. The next prime is 638666837.

It is a happy number.

638666836 is nontrivially palindromic in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638666837) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 722851 + ... + 723733.

Almost surely, 2^638666836 is an apocalyptic number.

It is an amenable number.

638666836 is a deficient number, since it is larger than the sum of its proper divisors (581111724).

638666836 is a wasteful number, since it uses less digits than its factorization.

638666836 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1244 (or 1242 counting only the distinct ones).

The product of its digits is 4478976, while the sum is 52.

The square root of 638666836 is about 25271.8585782684. The cubic root of 638666836 is about 861.1750819668.

The spelling of 638666836 in words is "six hundred thirty-eight million, six hundred sixty-six thousand, eight hundred thirty-six".