198808991 has 4 divisors (see below), whose sum is σ = 199999632. Its totient is φ = 197618352.

The previous prime is 198808979. The next prime is 198808993. The reversal of 198808991 is 199808891.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 199808891 = 47 ⋅4251253.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-198808991 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (198808993) 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, 595070 + ... + 595403.

It is an arithmetic number, because the mean of its divisors is an integer number (49999908).

Almost surely, 2^198808991 is an apocalyptic number.

198808991 is a deficient number, since it is larger than the sum of its proper divisors (1190641).

198808991 is a wasteful number, since it uses less digits than its factorization.

198808991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1190640.

The product of its (nonzero) digits is 373248, while the sum is 53.

The square root of 198808991 is about 14099.9642198128. The cubic root of 198808991 is about 583.6403918822.

The spelling of 198808991 in words is "one hundred ninety-eight million, eight hundred eight thousand, nine hundred ninety-one".