21011110979921 has 2 divisors, whose sum is σ = 21011110979922. Its totient is φ = 21011110979920.

The previous prime is 21011110979899. The next prime is 21011110979923. The reversal of 21011110979921 is 12997901111012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17647023098896 + 3364087881025 = 4200836^2 + 1834145^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21011110979921 is a prime.

It is a super-2 number, since 2×21011110979921² (a number of 27 digits) contains 22 as substring.

Together with 21011110979923, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21011110979923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505555489960 + 10505555489961.

It is an arithmetic number, because the mean of its divisors is an integer number (10505555489961).

Almost surely, 2^{21011110979921} is an apocalyptic number.

It is an amenable number.

21011110979921 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011110979921 is an equidigital number, since it uses as much as digits as its factorization.

21011110979921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20412, while the sum is 44.

The spelling of 21011110979921 in words is "twenty-one trillion, eleven billion, one hundred ten million, nine hundred seventy-nine thousand, nine hundred twenty-one".