199998661 has 2 divisors, whose sum is σ = 199998662. Its totient is φ = 199998660.

The previous prime is 199998649. The next prime is 199998707. The reversal of 199998661 is 166899991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 180364900 + 19633761 = 13430^2 + 4431^2 .

It is a cyclic number.

It is not a de Polignac number, because 199998661 - 2¹⁵ = 199965893 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 199998596 and 199998605.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (199999661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99999330 + 99999331.

It is an arithmetic number, because the mean of its divisors is an integer number (99999331).

Almost surely, 2^199998661 is an apocalyptic number.

It is an amenable number.

199998661 is a deficient number, since it is larger than the sum of its proper divisors (1).

199998661 is an equidigital number, since it uses as much as digits as its factorization.

199998661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1889568, while the sum is 58.

The square root of 199998661 is about 14142.0882828527. The cubic root of 199998661 is about 584.8022425531.

The spelling of 199998661 in words is "one hundred ninety-nine million, nine hundred ninety-eight thousand, six hundred sixty-one".