21011212091 has 2 divisors, whose sum is σ = 21011212092. Its totient is φ = 21011212090.

The previous prime is 21011212069. The next prime is 21011212093. The reversal of 21011212091 is 19021211012.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21011212091 is a prime.

Together with 21011212093, 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 (21011212093) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505606045 + 10505606046.

It is an arithmetic number, because the mean of its divisors is an integer number (10505606046).

Almost surely, 2^21011212091 is an apocalyptic number.

21011212091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011212091 is an equidigital number, since it uses as much as digits as its factorization.

21011212091 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 72, while the sum is 20.

The spelling of 21011212091 in words is "twenty-one billion, eleven million, two hundred twelve thousand, ninety-one".