666789 has 8 divisors (see below), whose sum is σ = 908160. Its totient is φ = 434976.

The previous prime is 666773. The next prime is 666811. The reversal of 666789 is 987666.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 666789 - 2⁴ = 666773 is a prime.

It is a plaindrome in base 10.

It is a self number, because there is not a number n which added to its sum of digits gives 666789.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666749) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2224 + ... + 2505.

It is an arithmetic number, because the mean of its divisors is an integer number (113520).

2⁶⁶⁶⁷⁸⁹ is an apocalyptic number.

It is an amenable number.

666789 is a deficient number, since it is larger than the sum of its proper divisors (241371).

666789 is a wasteful number, since it uses less digits than its factorization.

666789 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4779.

The product of its digits is 108864, while the sum is 42.

The square root of 666789 is about 816.5714910527. The cubic root of 666789 is about 87.3633895473.

It can be divided in two parts, 6 and 66789, that added together give a triangular number (66795 = T₃₆₅).

The spelling of 666789 in words is "six hundred sixty-six thousand, seven hundred eighty-nine".