21110981 has 2 divisors, whose sum is σ = 21110982. Its totient is φ = 21110980.

The previous prime is 21110977. The next prime is 21110989. The reversal of 21110981 is 18901112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16120225 + 4990756 = 4015^2 + 2234^2 .

It is a cyclic number.

It is not a de Polignac number, because 21110981 - 2² = 21110977 is a prime.

It is a super-2 number, since 2×21110981² = 891347037564722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21110989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10555490 + 10555491.

It is an arithmetic number, because the mean of its divisors is an integer number (10555491).

Almost surely, 2^21110981 is an apocalyptic number.

It is an amenable number.

21110981 is a deficient number, since it is larger than the sum of its proper divisors (1).

21110981 is an equidigital number, since it uses as much as digits as its factorization.

21110981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 144, while the sum is 23.

The square root of 21110981 is about 4594.6687584634. The cubic root of 21110981 is about 276.3775769398.

The spelling of 21110981 in words is "twenty-one million, one hundred ten thousand, nine hundred eighty-one".