198115921 has 4 divisors (see below), whose sum is σ = 202723312. Its totient is φ = 193508532.

The previous prime is 198115889. The next prime is 198115933. The reversal of 198115921 is 129511891.

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, and also an emirpimes, since its reverse is a distinct semiprime: 129511891 = 103 ⋅1257397.

It is a cyclic number.

It is not a de Polignac number, because 198115921 - 2⁵ = 198115889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (198115991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2303631 + ... + 2303716.

It is an arithmetic number, because the mean of its divisors is an integer number (50680828).

Almost surely, 2^198115921 is an apocalyptic number.

It is an amenable number.

198115921 is a deficient number, since it is larger than the sum of its proper divisors (4607391).

198115921 is an equidigital number, since it uses as much as digits as its factorization.

198115921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4607390.

The product of its digits is 6480, while the sum is 37.

The square root of 198115921 is about 14075.3657501324. The cubic root of 198115921 is about 582.9613907215.

The spelling of 198115921 in words is "one hundred ninety-eight million, one hundred fifteen thousand, nine hundred twenty-one".