198665809 has 4 divisors (see below), whose sum is σ = 198722160. Its totient is φ = 198609460.

The previous prime is 198665773. The next prime is 198665813. The reversal of 198665809 is 908566891.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 908566891 = 3331 ⋅272761.

It is a cyclic number.

It is not a de Polignac number, because 198665809 - 2⁷ = 198665681 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (198665209) 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, 22507 + ... + 30064.

It is an arithmetic number, because the mean of its divisors is an integer number (49680540).

Almost surely, 2^198665809 is an apocalyptic number.

It is an amenable number.

198665809 is a deficient number, since it is larger than the sum of its proper divisors (56351).

198665809 is an equidigital number, since it uses as much as digits as its factorization.

198665809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56350.

The product of its (nonzero) digits is 933120, while the sum is 52.

The square root of 198665809 is about 14094.8859165302. The cubic root of 198665809 is about 583.5002458594.

The spelling of 198665809 in words is "one hundred ninety-eight million, six hundred sixty-five thousand, eight hundred nine".