21011995091 has 2 divisors, whose sum is σ = 21011995092. Its totient is φ = 21011995090.

The previous prime is 21011995001. The next prime is 21011995093. The reversal of 21011995091 is 19059911012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21011995091 - 2³⁰ = 19938253267 is a prime.

Together with 21011995093, 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 (21011995093) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505997545 + 10505997546.

It is an arithmetic number, because the mean of its divisors is an integer number (10505997546).

Almost surely, 2^21011995091 is an apocalyptic number.

21011995091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011995091 is an equidigital number, since it uses as much as digits as its factorization.

21011995091 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7290, while the sum is 38.

The spelling of 21011995091 in words is "twenty-one billion, eleven million, nine hundred ninety-five thousand, ninety-one".