21111110981 has 2 divisors, whose sum is σ = 21111110982. Its totient is φ = 21111110980.

The previous prime is 21111110959. The next prime is 21111111023. The reversal of 21111110981 is 18901111112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17342256100 + 3768854881 = 131690^2 + 61391^2 .

It is a cyclic number.

It is not a de Polignac number, because 21111110981 - 2²⁶ = 21044002117 is a prime.

It is a super-2 number, since 2×21111110981² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21111110981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21111100981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10555555490 + 10555555491.

It is an arithmetic number, because the mean of its divisors is an integer number (10555555491).

Almost surely, 2^21111110981 is an apocalyptic number.

It is an amenable number.

21111110981 is a deficient number, since it is larger than the sum of its proper divisors (1).

21111110981 is an equidigital number, since it uses as much as digits as its factorization.

21111110981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 144, while the sum is 26.

The spelling of 21111110981 in words is "twenty-one billion, one hundred eleven million, one hundred ten thousand, nine hundred eighty-one".