121999991 has 2 divisors, whose sum is σ = 121999992. Its totient is φ = 121999990.

The previous prime is 121999967. The next prime is 122000003. The reversal of 121999991 is 199999121.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 121999991 - 2¹⁴ = 121983607 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (121999951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 60999995 + 60999996.

It is an arithmetic number, because the mean of its divisors is an integer number (60999996).

Almost surely, 2^121999991 is an apocalyptic number.

121999991 is a deficient number, since it is larger than the sum of its proper divisors (1).

121999991 is an equidigital number, since it uses as much as digits as its factorization.

121999991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 118098, while the sum is 50.

The square root of 121999991 is about 11045.3606097764. The cubic root of 121999991 is about 495.9675541883.

The spelling of 121999991 in words is "one hundred twenty-one million, nine hundred ninety-nine thousand, nine hundred ninety-one".