666986999 has 4 divisors (see below), whose sum is σ = 762270864. Its totient is φ = 571703136.

The previous prime is 666986987. The next prime is 666987019. The reversal of 666986999 is 999689666.

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 666986999 - 2²⁰ = 665938423 is a prime.

666986999 is a strobogrammatic number because it is the same when read upside-down.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666986899) 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, 47641922 + ... + 47641935.

It is an arithmetic number, because the mean of its divisors is an integer number (190567716).

Almost surely, 2^666986999 is an apocalyptic number.

666986999 is a deficient number, since it is larger than the sum of its proper divisors (95283865).

666986999 is an equidigital number, since it uses as much as digits as its factorization.

666986999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95283864.

The product of its digits is 68024448, while the sum is 68.

The square root of 666986999 is about 25826.0914386982. The cubic root of 666986999 is about 873.7203603665.

The spelling of 666986999 in words is "six hundred sixty-six million, nine hundred eighty-six thousand, nine hundred ninety-nine".