198821 has 4 divisors (see below), whose sum is σ = 227232. Its totient is φ = 170412.

The previous prime is 198817. The next prime is 198823. The reversal of 198821 is 128891.

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: 128891 = 7 ⋅18413.

It is a cyclic number.

It is not a de Polignac number, because 198821 - 2² = 198817 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (198823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14195 + ... + 14208.

It is an arithmetic number, because the mean of its divisors is an integer number (56808).

2¹⁹⁸⁸²¹ is an apocalyptic number.

It is an amenable number.

198821 is a deficient number, since it is larger than the sum of its proper divisors (28411).

198821 is an equidigital number, since it uses as much as digits as its factorization.

198821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28410.

The product of its digits is 1152, while the sum is 29.

The square root of 198821 is about 445.8934850387. The cubic root of 198821 is about 58.3652143189.

The spelling of 198821 in words is "one hundred ninety-eight thousand, eight hundred twenty-one".