198805991 has 4 divisors (see below), whose sum is σ = 205661400. Its totient is φ = 191950584.

The previous prime is 198805969. The next prime is 198806009. The reversal of 198805991 is 199508891.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 199508891 = 79 ⋅2525429.

It is a cyclic number.

It is not a de Polignac number, because 198805991 - 2¹⁰ = 198804967 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 (198805931) by changing a digit.

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, 3427661 + ... + 3427718.

It is an arithmetic number, because the mean of its divisors is an integer number (51415350).

Almost surely, 2^198805991 is an apocalyptic number.

198805991 is a deficient number, since it is larger than the sum of its proper divisors (6855409).

198805991 is an equidigital number, since it uses as much as digits as its factorization.

198805991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6855408.

The product of its (nonzero) digits is 233280, while the sum is 50.

The square root of 198805991 is about 14099.8578361627. The cubic root of 198805991 is about 583.6374561834.

The spelling of 198805991 in words is "one hundred ninety-eight million, eight hundred five thousand, nine hundred ninety-one".