199666 has 4 divisors (see below), whose sum is σ = 299502. Its totient is φ = 99832.

The previous prime is 199657. The next prime is 199669. The reversal of 199666 is 666991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 666991 = 13 ⋅51307.

It can be written as a sum of positive squares in only one way, i.e., 184041 + 15625 = 429^2 + 125^2 .

It is not an unprimeable number, because it can be changed into a prime (199669) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 49915 + ... + 49918.

2¹⁹⁹⁶⁶⁶ is an apocalyptic number.

199666 is a deficient number, since it is larger than the sum of its proper divisors (99836).

199666 is an equidigital number, since it uses as much as digits as its factorization.

199666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99835.

The product of its digits is 17496, while the sum is 37.

The square root of 199666 is about 446.8400161131. The cubic root of 199666 is about 58.4477825615.

The spelling of 199666 in words is "one hundred ninety-nine thousand, six hundred sixty-six".