121212111991 has 2 divisors, whose sum is σ = 121212111992. Its totient is φ = 121212111990.

The previous prime is 121212111989. The next prime is 121212112001. The reversal of 121212111991 is 199111212121.

It is a weak prime.

It is an emirp because it is prime and its reverse (199111212121) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 121212111991 - 2¹ = 121212111989 is a prime.

Together with 121212111989, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (121212111931) 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, 60606055995 + 60606055996.

It is an arithmetic number, because the mean of its divisors is an integer number (60606055996).

Almost surely, 2^121212111991 is an apocalyptic number.

121212111991 is a deficient number, since it is larger than the sum of its proper divisors (1).

121212111991 is an equidigital number, since it uses as much as digits as its factorization.

121212111991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 648, while the sum is 31.

The spelling of 121212111991 in words is "one hundred twenty-one billion, two hundred twelve million, one hundred eleven thousand, nine hundred ninety-one".