638691869123 has 64 divisors (see below), whose sum is σ = 847348604928. Its totient is φ = 466719390720.

The previous prime is 638691869119. The next prime is 638691869131. The reversal of 638691869123 is 321968196836.

It is a Cunningham number, because it is equal to 799182²-1.

It is not a de Polignac number, because 638691869123 - 2² = 638691869119 is a prime.

Its product of digits (20155392) is a multiple of the sum of its prime divisors (34992).

It is not an unprimeable number, because it can be changed into a prime (638691869623) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 18363836 + ... + 18398582.

It is an arithmetic number, because the mean of its divisors is an integer number (13239821952).

Almost surely, 2^638691869123 is an apocalyptic number.

638691869123 is a deficient number, since it is larger than the sum of its proper divisors (208656735805).

638691869123 is a wasteful number, since it uses less digits than its factorization.

638691869123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34992.

The product of its digits is 20155392, while the sum is 62.

The spelling of 638691869123 in words is "six hundred thirty-eight billion, six hundred ninety-one million, eight hundred sixty-nine thousand, one hundred twenty-three".