121913085991 has 4 divisors (see below), whose sum is σ = 121913785584. Its totient is φ = 121912386400.

The previous prime is 121913085869. The next prime is 121913086003. The reversal of 121913085991 is 199580319121.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 121913085991 - 2²¹ = 121910988839 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (121913085191) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 143286 + ... + 514156.

It is an arithmetic number, because the mean of its divisors is an integer number (30478446396).

Almost surely, 2^121913085991 is an apocalyptic number.

121913085991 is a deficient number, since it is larger than the sum of its proper divisors (699593).

121913085991 is an equidigital number, since it uses as much as digits as its factorization.

121913085991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 699592.

The product of its (nonzero) digits is 174960, while the sum is 49.

The spelling of 121913085991 in words is "one hundred twenty-one billion, nine hundred thirteen million, eighty-five thousand, nine hundred ninety-one".