199999661 has 2 divisors, whose sum is σ = 199999662. Its totient is φ = 199999660.

The previous prime is 199999649. The next prime is 199999673. The reversal of 199999661 is 166999991.

It is a balanced prime because it is at equal distance from previous prime (199999649) and next prime (199999673).

It can be written as a sum of positive squares in only one way, i.e., 187854436 + 12145225 = 13706^2 + 3485^2 .

It is an emirp because it is prime and its reverse (166999991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 199999661 - 2¹⁰ = 199998637 is a prime.

It is a super-2 number, since 2×199999661² = 79999728800229842, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 199999661.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (199999601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99999830 + 99999831.

It is an arithmetic number, because the mean of its divisors is an integer number (99999831).

Almost surely, 2^199999661 is an apocalyptic number.

It is an amenable number.

199999661 is a deficient number, since it is larger than the sum of its proper divisors (1).

199999661 is an equidigital number, since it uses as much as digits as its factorization.

199999661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2125764, while the sum is 59.

The square root of 199999661 is about 14142.1236382659. The cubic root of 199999661 is about 584.8032172284.

The spelling of 199999661 in words is "one hundred ninety-nine million, nine hundred ninety-nine thousand, six hundred sixty-one".