21102091 has 2 divisors, whose sum is σ = 21102092. Its totient is φ = 21102090.

The previous prime is 21102089. The next prime is 21102101. The reversal of 21102091 is 19020112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21102091 - 2¹ = 21102089 is a prime.

Together with 21102089, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21102071) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10551045 + 10551046.

It is an arithmetic number, because the mean of its divisors is an integer number (10551046).

Almost surely, 2^21102091 is an apocalyptic number.

21102091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21102091 is an equidigital number, since it uses as much as digits as its factorization.

21102091 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 36, while the sum is 16.

The square root of 21102091 is about 4593.7012310336. The cubic root of 21102091 is about 276.3387765697.

The spelling of 21102091 in words is "twenty-one million, one hundred two thousand, ninety-one".