21010121209991 has 2 divisors, whose sum is σ = 21010121209992. Its totient is φ = 21010121209990.

The previous prime is 21010121209981. The next prime is 21010121210041. The reversal of 21010121209991 is 19990212101012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21010121209991 - 2⁶ = 21010121209927 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21010121209981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505060604995 + 10505060604996.

It is an arithmetic number, because the mean of its divisors is an integer number (10505060604996).

Almost surely, 2^{21010121209991} is an apocalyptic number.

21010121209991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21010121209991 is an equidigital number, since it uses as much as digits as its factorization.

21010121209991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5832, while the sum is 38.

The spelling of 21010121209991 in words is "twenty-one trillion, ten billion, one hundred twenty-one million, two hundred nine thousand, nine hundred ninety-one".