638865516566 has 4 divisors (see below), whose sum is σ = 958298274852. Its totient is φ = 319432758282.

The previous prime is 638865516563. The next prime is 638865516589. The reversal of 638865516566 is 665615568836.

It is a semiprime because it is the product of two primes.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638865516563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 159716379140 + ... + 159716379143.

It is an arithmetic number, because the mean of its divisors is an integer number (239574568713).

Almost surely, 2^638865516566 is an apocalyptic number.

638865516566 is a deficient number, since it is larger than the sum of its proper divisors (319432758286).

638865516566 is a wasteful number, since it uses less digits than its factorization.

638865516566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 319432758285.

The product of its digits is 186624000, while the sum is 65.

The spelling of 638865516566 in words is "six hundred thirty-eight billion, eight hundred sixty-five million, five hundred sixteen thousand, five hundred sixty-six".