199198198891 has 4 divisors (see below), whose sum is σ = 199199145672. Its totient is φ = 199197252112.

The previous prime is 199198198867. The next prime is 199198198951. The reversal of 199198198891 is 198891891991.

199198198891 is a nontrivial binomial coefficient, being equal to C(631187, 2).

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a de Polignac number, because none of the positive numbers 2^k-199198198891 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (199198195891) 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, 1 + ... + 631186.

It is an arithmetic number, because the mean of its divisors is an integer number (49799786418).

Almost surely, 2^199198198891 is an apocalyptic number.

199198198891 is the 631186-th triangular number.

199198198891 is the 210396-th centered nonagonal number.

199198198891 is a deficient number, since it is larger than the sum of its proper divisors (946781).

199198198891 is an equidigital number, since it uses as much as digits as its factorization.

199198198891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 946780.

The product of its digits is 30233088, while the sum is 73.

The spelling of 199198198891 in words is "one hundred ninety-nine billion, one hundred ninety-eight million, one hundred ninety-eight thousand, eight hundred ninety-one".