21006688865 has 32 divisors (see below), whose sum is σ = 26121263616. Its totient is φ = 16206704640.

The previous prime is 21006688799. The next prime is 21006688867. The reversal of 21006688865 is 56888660012.

It is not a de Polignac number, because 21006688865 - 2⁸ = 21006688609 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21006688867) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 14761544 + ... + 14762966.

It is an arithmetic number, because the mean of its divisors is an integer number (816289488).

Almost surely, 2^21006688865 is an apocalyptic number.

It is an amenable number.

21006688865 is a deficient number, since it is larger than the sum of its proper divisors (5114574751).

21006688865 is a wasteful number, since it uses less digits than its factorization.

21006688865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2249.

The product of its (nonzero) digits is 1105920, while the sum is 50.

The spelling of 21006688865 in words is "twenty-one billion, six million, six hundred eighty-eight thousand, eight hundred sixty-five".