198639891 has 32 divisors (see below), whose sum is σ = 311040000. Its totient is φ = 125034624.

The previous prime is 198639887. The next prime is 198639893. The reversal of 198639891 is 198936891.

It is not a de Polignac number, because 198639891 - 2² = 198639887 is a prime.

It is not an unprimeable number, because it can be changed into a prime (198639893) 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 31 ways as a sum of consecutive naturals, for example, 47035 + ... + 51083.

It is an arithmetic number, because the mean of its divisors is an integer number (9720000).

Almost surely, 2^198639891 is an apocalyptic number.

198639891 is a deficient number, since it is larger than the sum of its proper divisors (112400109).

198639891 is a wasteful number, since it uses less digits than its factorization.

198639891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4160 (or 4154 counting only the distinct ones).

The product of its digits is 839808, while the sum is 54.

The square root of 198639891 is about 14093.9664750559. The cubic root of 198639891 is about 583.4748702178.

The spelling of 198639891 in words is "one hundred ninety-eight million, six hundred thirty-nine thousand, eight hundred ninety-one".