198721 has 4 divisors (see below), whose sum is σ = 209200. Its totient is φ = 188244.

The previous prime is 198719. The next prime is 198733. The reversal of 198721 is 127891.

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: 127891 = 17 ⋅7523.

It is a cyclic number.

It is not a de Polignac number, because 198721 - 2¹ = 198719 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 198721.

It is not an unprimeable number, because it can be changed into a prime (198701) 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, 5211 + ... + 5248.

It is an arithmetic number, because the mean of its divisors is an integer number (52300).

2¹⁹⁸⁷²¹ is an apocalyptic number.

It is an amenable number.

198721 is a deficient number, since it is larger than the sum of its proper divisors (10479).

198721 is a wasteful number, since it uses less digits than its factorization.

198721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10478.

The product of its digits is 1008, while the sum is 28.

The square root of 198721 is about 445.7813365317. The cubic root of 198721 is about 58.3554274583.

It can be divided in two parts, 198 and 721, that added together give a palindrome (919).

The spelling of 198721 in words is "one hundred ninety-eight thousand, seven hundred twenty-one".