666999 has 12 divisors (see below), whose sum is σ = 989976. Its totient is φ = 432432.

The previous prime is 666989. The next prime is 667013. The reversal of 666999 is 999666.

It is not a de Polignac number, because 666999 - 2⁴ = 666983 is a prime.

666999 is a strobogrammatic number because it is the same when read upside-down.

666999 is a modest number, since divided by 999 gives 666 as remainder.

It is a plaindrome in base 10.

It is a zygodrome in base 10.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 666999.

It is not an unprimeable number, because it can be changed into a prime (666929) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 669 + ... + 1334.

It is an arithmetic number, because the mean of its divisors is an integer number (82498).

2⁶⁶⁶⁹⁹⁹ is an apocalyptic number.

666999 is a deficient number, since it is larger than the sum of its proper divisors (322977).

666999 is a wasteful number, since it uses less digits than its factorization.

666999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2046 (or 2043 counting only the distinct ones).

The product of its digits is 157464, while the sum is 45.

The square root of 666999 is about 816.7000673442. The cubic root of 666999 is about 87.3725600576.

The spelling of 666999 in words is "six hundred sixty-six thousand, nine hundred ninety-nine".