666899 has 4 divisors (see below), whose sum is σ = 679536. Its totient is φ = 654264.

The previous prime is 666889. The next prime is 666901. The reversal of 666899 is 998666.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 666899 - 2⁸ = 666643 is a prime.

It is a Duffinian number.

It is a plaindrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (666829) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6239 + ... + 6344.

It is an arithmetic number, because the mean of its divisors is an integer number (169884).

2⁶⁶⁶⁸⁹⁹ is an apocalyptic number.

666899 is a deficient number, since it is larger than the sum of its proper divisors (12637).

666899 is a wasteful number, since it uses less digits than its factorization.

666899 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12636.

The product of its digits is 139968, while the sum is 44.

The square root of 666899 is about 816.6388430634. The cubic root of 666899 is about 87.3681933881.

The spelling of 666899 in words is "six hundred sixty-six thousand, eight hundred ninety-nine".