638563855821 has 8 divisors (see below), whose sum is σ = 859375656864. Its totient is φ = 421730646000.

The previous prime is 638563855817. The next prime is 638563855823. The reversal of 638563855821 is 128558365836.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 638563855821 - 2² = 638563855817 is a prime.

It is a Smith number, since the sum of its digits (60) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638563855823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 994647430 + ... + 994648071.

It is an arithmetic number, because the mean of its divisors is an integer number (107421957108).

Almost surely, 2^638563855821 is an apocalyptic number.

It is an amenable number.

638563855821 is a deficient number, since it is larger than the sum of its proper divisors (220811801043).

638563855821 is a wasteful number, since it uses less digits than its factorization.

638563855821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1989295611.

The product of its digits is 41472000, while the sum is 60.

The spelling of 638563855821 in words is "six hundred thirty-eight billion, five hundred sixty-three million, eight hundred fifty-five thousand, eight hundred twenty-one".