198909909891 has 48 divisors (see below), whose sum is σ = 358445937408. Its totient is φ = 103261780800.

The previous prime is 198909909859. The next prime is 198909909899.

198909909891 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 198909909891 - 2⁵ = 198909909859 is a prime.

It is not an unprimeable number, because it can be changed into a prime (198909909899) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 967245 + ... + 1154721.

It is an arithmetic number, because the mean of its divisors is an integer number (7467623696).

Almost surely, 2^198909909891 is an apocalyptic number.

198909909891 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

198909909891 is a deficient number, since it is larger than the sum of its proper divisors (159536027517).

198909909891 is a wasteful number, since it uses less digits than its factorization.

198909909891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 189032 (or 189029 counting only the distinct ones).

The product of its (nonzero) digits is 34012224, while the sum is 72.

The spelling of 198909909891 in words is "one hundred ninety-eight billion, nine hundred nine million, nine hundred nine thousand, eight hundred ninety-one".