21911 has 2 divisors, whose sum is σ = 21912. Its totient is φ = 21910.

The previous prime is 21893. The next prime is 21929. The reversal of 21911 is 11912.

It is a m-pointer prime, because the next prime (21929) can be obtained adding 21911 to its product of digits (18).

It is a balanced prime because it is at equal distance from previous prime (21893) and next prime (21929).

It is a cyclic number.

It is not a de Polignac number, because 21911 - 2¹⁰ = 20887 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10955 + 10956.

It is an arithmetic number, because the mean of its divisors is an integer number (10956).

2²¹⁹¹¹ is an apocalyptic number.

21911 is a deficient number, since it is larger than the sum of its proper divisors (1).

21911 is an equidigital number, since it uses as much as digits as its factorization.

21911 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18, while the sum is 14.

The square root of 21911 is about 148.0236467596. The cubic root of 21911 is about 27.9825571633.

Subtracting from 21911 its reverse (11912), we obtain a palindrome (9999).

The spelling of 21911 in words is "twenty-one thousand, nine hundred eleven".