121991615 has 4 divisors (see below), whose sum is σ = 146389944. Its totient is φ = 97593288.

The previous prime is 121991599. The next prime is 121991621. The reversal of 121991615 is 516199121.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 516199121 = 953 ⋅541657.

It is a cyclic number.

It is not a de Polignac number, because 121991615 - 2⁴ = 121991599 is a prime.

It is a Duffinian number.

It is a zygodrome in base 3.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12199157 + ... + 12199166.

It is an arithmetic number, because the mean of its divisors is an integer number (36597486).

Almost surely, 2^121991615 is an apocalyptic number.

121991615 is a deficient number, since it is larger than the sum of its proper divisors (24398329).

121991615 is an equidigital number, since it uses as much as digits as its factorization.

121991615 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24398328.

The product of its digits is 4860, while the sum is 35.

The square root of 121991615 is about 11044.9814395498. The cubic root of 121991615 is about 495.9562035883.

The spelling of 121991615 in words is "one hundred twenty-one million, nine hundred ninety-one thousand, six hundred fifteen".