199716721 has 2 divisors, whose sum is σ = 199716722. Its totient is φ = 199716720.

The previous prime is 199716719. The next prime is 199716739. The reversal of 199716721 is 127617991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 164480625 + 35236096 = 12825^2 + 5936^2 .

It is a cyclic number.

It is not a de Polignac number, because 199716721 - 2¹ = 199716719 is a prime.

Together with 199716719, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (199716791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99858360 + 99858361.

It is an arithmetic number, because the mean of its divisors is an integer number (99858361).

Almost surely, 2^199716721 is an apocalyptic number.

It is an amenable number.

199716721 is a deficient number, since it is larger than the sum of its proper divisors (1).

199716721 is an equidigital number, since it uses as much as digits as its factorization.

199716721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 47628, while the sum is 43.

The square root of 199716721 is about 14132.1166496742. The cubic root of 199716721 is about 584.5273129087.

The spelling of 199716721 in words is "one hundred ninety-nine million, seven hundred sixteen thousand, seven hundred twenty-one".