199891 has 4 divisors (see below), whose sum is σ = 204192. Its totient is φ = 195592.

The previous prime is 199889. The next prime is 199909. The reversal of 199891 is 198991.

199891 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 198991 = 13 ⋅15307.

It is a cyclic number.

It is not a de Polignac number, because 199891 - 2¹ = 199889 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 199891.

It is not an unprimeable number, because it can be changed into a prime (199811) 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, 2080 + ... + 2173.

It is an arithmetic number, because the mean of its divisors is an integer number (51048).

2¹⁹⁹⁸⁹¹ is an apocalyptic number.

199891 is a deficient number, since it is larger than the sum of its proper divisors (4301).

199891 is an equidigital number, since it uses as much as digits as its factorization.

199891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4300.

The product of its digits is 5832, while the sum is 37.

The square root of 199891 is about 447.0917131865. The cubic root of 199891 is about 58.4697289025.

Subtracting from 199891 its reverse (198991), we obtain a square (900 = 30²).

The spelling of 199891 in words is "one hundred ninety-nine thousand, eight hundred ninety-one".