199821 has 8 divisors (see below), whose sum is σ = 272800. Its totient is φ = 130032.

The previous prime is 199819. The next prime is 199831. The reversal of 199821 is 128991.

199821 is nontrivially palindromic in base 12.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 199821 - 2¹ = 199819 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 (199811) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 646 + ... + 903.

It is an arithmetic number, because the mean of its divisors is an integer number (34100).

2¹⁹⁹⁸²¹ is an apocalyptic number.

It is an amenable number.

199821 is a deficient number, since it is larger than the sum of its proper divisors (72979).

199821 is a wasteful number, since it uses less digits than its factorization.

199821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1595.

The product of its digits is 1296, while the sum is 30.

The square root of 199821 is about 447.0134226173. The cubic root of 199821 is about 58.4629029176.

The spelling of 199821 in words is "one hundred ninety-nine thousand, eight hundred twenty-one".