21660704991 has 40 divisors (see below), whose sum is σ = 33190106400. Its totient is φ = 14072505408.

The previous prime is 21660704977. The next prime is 21660704999. The reversal of 21660704991 is 19940706612.

It is not a de Polignac number, because 21660704991 - 2³⁰ = 20586963167 is a prime.

It is a super-2 number, since 2×21660704991² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21660704999) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 622726 + ... + 656588.

It is an arithmetic number, because the mean of its divisors is an integer number (829752660).

Almost surely, 2^21660704991 is an apocalyptic number.

21660704991 is a deficient number, since it is larger than the sum of its proper divisors (11529401409).

21660704991 is a wasteful number, since it uses less digits than its factorization.

21660704991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34077 (or 34068 counting only the distinct ones).

The product of its (nonzero) digits is 163296, while the sum is 45.

The spelling of 21660704991 in words is "twenty-one billion, six hundred sixty million, seven hundred four thousand, nine hundred ninety-one".