21115091 has 2 divisors, whose sum is σ = 21115092. Its totient is φ = 21115090.

The previous prime is 21115063. The next prime is 21115093. The reversal of 21115091 is 19051112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21115091 - 2⁶ = 21115027 is a prime.

Together with 21115093, 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 (21115093) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10557545 + 10557546.

It is an arithmetic number, because the mean of its divisors is an integer number (10557546).

Almost surely, 2^21115091 is an apocalyptic number.

21115091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21115091 is an equidigital number, since it uses as much as digits as its factorization.

21115091 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 90, while the sum is 20.

The square root of 21115091 is about 4595.1159941834. The cubic root of 21115091 is about 276.3955113366.

The spelling of 21115091 in words is "twenty-one million, one hundred fifteen thousand, ninety-one".