1666999 has 2 divisors, whose sum is σ = 1667000. Its totient is φ = 1666998.

The previous prime is 1666991. The next prime is 1667033. The reversal of 1666999 is 9996661.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1666999 - 2³ = 1666991 is a prime.

It is a plaindrome in base 10.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1666991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 833499 + 833500.

It is an arithmetic number, because the mean of its divisors is an integer number (833500).

2^1666999 is an apocalyptic number.

1666999 is a deficient number, since it is larger than the sum of its proper divisors (1).

1666999 is an equidigital number, since it uses as much as digits as its factorization.

1666999 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 157464, while the sum is 46.

The square root of 1666999 is about 1291.1231544667. The cubic root of 1666999 is about 118.5709901207.

The spelling of 1666999 in words is "one million, six hundred sixty-six thousand, nine hundred ninety-nine".