199999721 has 2 divisors, whose sum is σ = 199999722. Its totient is φ = 199999720.

The previous prime is 199999703. The next prime is 199999739. The reversal of 199999721 is 127999991.

It is a balanced prime because it is at equal distance from previous prime (199999703) and next prime (199999739).

It can be written as a sum of positive squares in only one way, i.e., 153487321 + 46512400 = 12389^2 + 6820^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-199999721 is a prime.

It is not a weakly prime, because it can be changed into another prime (199939721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99999860 + 99999861.

It is an arithmetic number, because the mean of its divisors is an integer number (99999861).

Almost surely, 2^199999721 is an apocalyptic number.

It is an amenable number.

199999721 is a deficient number, since it is larger than the sum of its proper divisors (1).

199999721 is an equidigital number, since it uses as much as digits as its factorization.

199999721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 826686, while the sum is 56.

The square root of 199999721 is about 14142.1257595879. The cubic root of 199999721 is about 584.8032757088.

The spelling of 199999721 in words is "one hundred ninety-nine million, nine hundred ninety-nine thousand, seven hundred twenty-one".