21731796755991 has 20 divisors (see below), whose sum is σ = 37101197990032. Its totient is φ = 12418169574528.

The previous prime is 21731796755969. The next prime is 21731796756083. The reversal of 21731796755991 is 19955769713712.

21731796755991 is a `hidden beast` number, since 2 + 1 + 7 + 3 + 1 + 7 + 9 + 67 + 559 + 9 + 1 = 666.

It is not a de Polignac number, because 21731796755991 - 2⁵ = 21731796755959 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 (21731796705991) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 19163841370 + ... + 19163842503.

Almost surely, 2^{21731796755991} is an apocalyptic number.

21731796755991 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21731796755991 is a deficient number, since it is larger than the sum of its proper divisors (15369401234041).

21731796755991 is an equidigital number, since it uses as much as digits as its factorization.

21731796755991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38327683892 (or 38327683883 counting only the distinct ones).

The product of its digits is 225042300, while the sum is 72.

The spelling of 21731796755991 in words is "twenty-one trillion, seven hundred thirty-one billion, seven hundred ninety-six million, seven hundred fifty-five thousand, nine hundred ninety-one".