21900091 has 2 divisors, whose sum is σ = 21900092. Its totient is φ = 21900090.

The previous prime is 21900059. The next prime is 21900107. The reversal of 21900091 is 19000912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21900091 - 2⁵ = 21900059 is a prime.

It is a super-2 number, since 2×21900091² = 959227971616562, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21900031) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10950045 + 10950046.

It is an arithmetic number, because the mean of its divisors is an integer number (10950046).

Almost surely, 2^21900091 is an apocalyptic number.

21900091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21900091 is an equidigital number, since it uses as much as digits as its factorization.

21900091 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 162, while the sum is 22.

The square root of 21900091 is about 4679.7533054639. The cubic root of 21900091 is about 279.7791242792.

The spelling of 21900091 in words is "twenty-one million, nine hundred thousand, ninety-one".