199985921 has 2 divisors, whose sum is σ = 199985922. Its totient is φ = 199985920.

The previous prime is 199985917. The next prime is 199985923. The reversal of 199985921 is 129589991.

199985921 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., 177848896 + 22137025 = 13336^2 + 4705^2 .

It is a cyclic number.

It is not a de Polignac number, because 199985921 - 2² = 199985917 is a prime.

Together with 199985923, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (199985923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99992960 + 99992961.

It is an arithmetic number, because the mean of its divisors is an integer number (99992961).

Almost surely, 2^199985921 is an apocalyptic number.

It is an amenable number.

199985921 is a deficient number, since it is larger than the sum of its proper divisors (1).

199985921 is an equidigital number, since it uses as much as digits as its factorization.

199985921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 524880, while the sum is 53.

The square root of 199985921 is about 14141.6378471519. The cubic root of 199985921 is about 584.7898249053.

The spelling of 199985921 in words is "one hundred ninety-nine million, nine hundred eighty-five thousand, nine hundred twenty-one".