121542921991 has 4 divisors (see below), whose sum is σ = 121555778184. Its totient is φ = 121530065800.

The previous prime is 121542921979. The next prime is 121542922003. The reversal of 121542921991 is 199129245121.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (121542921979) and next prime (121542922003).

It is a cyclic number.

It is not a de Polignac number, because 121542921991 - 2²⁵ = 121509367559 is a prime.

It is a super-2 number, since 2×121542921991² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (121542921901) 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, 6413905 + ... + 6432826.

It is an arithmetic number, because the mean of its divisors is an integer number (30388944546).

Almost surely, 2^121542921991 is an apocalyptic number.

121542921991 is a deficient number, since it is larger than the sum of its proper divisors (12856193).

121542921991 is an equidigital number, since it uses as much as digits as its factorization.

121542921991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12856192.

The product of its digits is 116640, while the sum is 46.

The spelling of 121542921991 in words is "one hundred twenty-one billion, five hundred forty-two million, nine hundred twenty-one thousand, nine hundred ninety-one".