20811868256691 has 32 divisors (see below), whose sum is σ = 31002740651520. Its totient is φ = 13797987269472.

The previous prime is 20811868256659. The next prime is 20811868256693. The reversal of 20811868256691 is 19665286811802.

20811868256691 is a `hidden beast` number, since 2 + 0 + 8 + 1 + 1 + 8 + 68 + 2 + 566 + 9 + 1 = 666.

It is not a de Polignac number, because 20811868256691 - 2⁵ = 20811868256659 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20811868256693) 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 31 ways as a sum of consecutive naturals, for example, 11058306 + ... + 12802728.

It is an arithmetic number, because the mean of its divisors is an integer number (968835645360).

Almost surely, 2^{20811868256691} is an apocalyptic number.

20811868256691 is a deficient number, since it is larger than the sum of its proper divisors (10190872394829).

20811868256691 is a wasteful number, since it uses less digits than its factorization.

20811868256691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1746872 (or 1746866 counting only the distinct ones).

The product of its (nonzero) digits is 19906560, while the sum is 63.

The spelling of 20811868256691 in words is "twenty trillion, eight hundred eleven billion, eight hundred sixty-eight million, two hundred fifty-six thousand, six hundred ninety-one".