666889 has 2 divisors, whose sum is σ = 666890. Its totient is φ = 666888.

The previous prime is 666871. The next prime is 666901. The reversal of 666889 is 988666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 537289 + 129600 = 733^2 + 360^2 .

It is a cyclic number.

It is not a de Polignac number, because 666889 - 2⁵ = 666857 is a prime.

It is a plaindrome in base 10.

It is not a weakly prime, because it can be changed into another prime (666829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333444 + 333445.

It is an arithmetic number, because the mean of its divisors is an integer number (333445).

2⁶⁶⁶⁸⁸⁹ is an apocalyptic number.

It is an amenable number.

666889 is a deficient number, since it is larger than the sum of its proper divisors (1).

666889 is an equidigital number, since it uses as much as digits as its factorization.

666889 is an evil number, because the sum of its binary digits is even.

The product of its digits is 124416, while the sum is 43.

The square root of 666889 is about 816.6327203829. The cubic root of 666889 is about 87.3677566971.

The spelling of 666889 in words is "six hundred sixty-six thousand, eight hundred eighty-nine".