21002221011991 has 2 divisors, whose sum is σ = 21002221011992. Its totient is φ = 21002221011990.

The previous prime is 21002221011983. The next prime is 21002221012013. The reversal of 21002221011991 is 19911012220012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21002221011991 - 2³ = 21002221011983 is a prime.

It is a super-3 number, since 3×21002221011991³ (a number of 41 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21002221011901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501110505995 + 10501110505996.

It is an arithmetic number, because the mean of its divisors is an integer number (10501110505996).

Almost surely, 2^{21002221011991} is an apocalyptic number.

21002221011991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21002221011991 is an equidigital number, since it uses as much as digits as its factorization.

21002221011991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1296, while the sum is 31.

The spelling of 21002221011991 in words is "twenty-one trillion, two billion, two hundred twenty-one million, eleven thousand, nine hundred ninety-one".