21117008639 has 4 divisors (see below), whose sum is σ = 21117656856. Its totient is φ = 21116360424.

The previous prime is 21117008629. The next prime is 21117008681. The reversal of 21117008639 is 93680071112.

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

It is a cyclic number.

It is not a de Polignac number, because 21117008639 - 2⁴ = 21117008623 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21117008629) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 272504 + ... + 341309.

It is an arithmetic number, because the mean of its divisors is an integer number (5279414214).

Almost surely, 2^21117008639 is an apocalyptic number.

21117008639 is a deficient number, since it is larger than the sum of its proper divisors (648217).

21117008639 is an equidigital number, since it uses as much as digits as its factorization.

21117008639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 648216.

The product of its (nonzero) digits is 18144, while the sum is 38.

The spelling of 21117008639 in words is "twenty-one billion, one hundred seventeen million, eight thousand, six hundred thirty-nine".