199921 has 2 divisors, whose sum is σ = 199922. Its totient is φ = 199920.

The previous prime is 199909. The next prime is 199931. The reversal of 199921 is 129991.

199921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 112896 + 87025 = 336^2 + 295^2 .

It is a cyclic number.

It is not a de Polignac number, because 199921 - 2⁵ = 199889 is a prime.

It is an Ulam number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (199931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99960 + 99961.

It is an arithmetic number, because the mean of its divisors is an integer number (99961).

2¹⁹⁹⁹²¹ is an apocalyptic number.

It is an amenable number.

199921 is a deficient number, since it is larger than the sum of its proper divisors (1).

199921 is an equidigital number, since it uses as much as digits as its factorization.

199921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1458, while the sum is 31.

The square root of 199921 is about 447.1252620911. The cubic root of 199921 is about 58.4726538368.

The spelling of 199921 in words is "one hundred ninety-nine thousand, nine hundred twenty-one".