21931711 has 2 divisors, whose sum is σ = 21931712. Its totient is φ = 21931710.

The previous prime is 21931709. The next prime is 21931727. The reversal of 21931711 is 11713912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21931711 - 2¹ = 21931709 is a prime.

Together with 21931709, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21931211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10965855 + 10965856.

It is an arithmetic number, because the mean of its divisors is an integer number (10965856).

Almost surely, 2^21931711 is an apocalyptic number.

21931711 is a deficient number, since it is larger than the sum of its proper divisors (1).

21931711 is an equidigital number, since it uses as much as digits as its factorization.

21931711 is an evil number, because the sum of its binary digits is even.

The product of its digits is 378, while the sum is 25.

The square root of 21931711 is about 4683.1304701022. The cubic root of 21931711 is about 279.9137106553.

The spelling of 21931711 in words is "twenty-one million, nine hundred thirty-one thousand, seven hundred eleven".