21118091 has 2 divisors, whose sum is σ = 21118092. Its totient is φ = 21118090.

The previous prime is 21118057. The next prime is 21118093. The reversal of 21118091 is 19081112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21118091 - 2¹⁰ = 21117067 is a prime.

Together with 21118093, 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 (21118093) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10559045 + 10559046.

It is an arithmetic number, because the mean of its divisors is an integer number (10559046).

Almost surely, 2^21118091 is an apocalyptic number.

21118091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21118091 is an equidigital number, since it uses as much as digits as its factorization.

21118091 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 23.

The square root of 21118091 is about 4595.4424161336. The cubic root of 21118091 is about 276.4086006680.

The spelling of 21118091 in words is "twenty-one million, one hundred eighteen thousand, ninety-one".