121991789 has 4 divisors (see below), whose sum is σ = 125927040. Its totient is φ = 118056540.

The previous prime is 121991767. The next prime is 121991797. The reversal of 121991789 is 987199121.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 121991789 - 2²⁰ = 120943213 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (121991729) 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, 1967579 + ... + 1967640.

It is an arithmetic number, because the mean of its divisors is an integer number (31481760).

Almost surely, 2^121991789 is an apocalyptic number.

It is an amenable number.

121991789 is a deficient number, since it is larger than the sum of its proper divisors (3935251).

121991789 is an equidigital number, since it uses as much as digits as its factorization.

121991789 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3935250.

The product of its digits is 81648, while the sum is 47.

The square root of 121991789 is about 11044.9893164276. The cubic root of 121991789 is about 495.9564393868.

The spelling of 121991789 in words is "one hundred twenty-one million, nine hundred ninety-one thousand, seven hundred eighty-nine".