121211001991 has 2 divisors, whose sum is σ = 121211001992. Its totient is φ = 121211001990.

The previous prime is 121211001971. The next prime is 121211002051. The reversal of 121211001991 is 199100112121.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 121211001991 - 2⁹ = 121211001479 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (121211001931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 60605500995 + 60605500996.

It is an arithmetic number, because the mean of its divisors is an integer number (60605500996).

Almost surely, 2^121211001991 is an apocalyptic number.

121211001991 is a deficient number, since it is larger than the sum of its proper divisors (1).

121211001991 is an equidigital number, since it uses as much as digits as its factorization.

121211001991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 324, while the sum is 28.

The spelling of 121211001991 in words is "one hundred twenty-one billion, two hundred eleven million, one thousand, nine hundred ninety-one".