198661 has 4 divisors (see below), whose sum is σ = 199692. Its totient is φ = 197632.

The previous prime is 198659. The next prime is 198673. The reversal of 198661 is 166891.

It is a happy number.

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, and also an emirpimes, since its reverse is a distinct semiprime: 166891 = 157 ⋅1063.

It can be written as a sum of positive squares in 2 ways, for example, as 112225 + 86436 = 335^2 + 294^2 .

It is a cyclic number.

It is not a de Polignac number, because 198661 - 2¹ = 198659 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (198641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 130 + ... + 643.

It is an arithmetic number, because the mean of its divisors is an integer number (49923).

2¹⁹⁸⁶⁶¹ is an apocalyptic number.

It is an amenable number.

198661 is a deficient number, since it is larger than the sum of its proper divisors (1031).

198661 is an equidigital number, since it uses as much as digits as its factorization.

198661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1030.

The product of its digits is 2592, while the sum is 31.

The square root of 198661 is about 445.7140338827. The cubic root of 198661 is about 58.3495537659.

The spelling of 198661 in words is "one hundred ninety-eight thousand, six hundred sixty-one".