198870991 has 4 divisors (see below), whose sum is σ = 216950184. Its totient is φ = 180791800.

The previous prime is 198870953. The next prime is 198871007. The reversal of 198870991 is 199078891.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 198870991 - 2⁹ = 198870479 is a prime.

It is a super-2 number, since 2×198870991² = 79099342122644162, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (198870691) 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, 9039580 + ... + 9039601.

It is an arithmetic number, because the mean of its divisors is an integer number (54237546).

Almost surely, 2^198870991 is an apocalyptic number.

198870991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

198870991 is a deficient number, since it is larger than the sum of its proper divisors (18079193).

198870991 is a wasteful number, since it uses less digits than its factorization.

198870991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18079192.

The product of its (nonzero) digits is 326592, while the sum is 52.

The square root of 198870991 is about 14102.1626355676. The cubic root of 198870991 is about 583.7010563810.

The spelling of 198870991 in words is "one hundred ninety-eight million, eight hundred seventy thousand, nine hundred ninety-one".