666989 has 2 divisors, whose sum is σ = 666990. Its totient is φ = 666988.

The previous prime is 666983. The next prime is 667013. The reversal of 666989 is 989666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 448900 + 218089 = 670^2 + 467^2 .

It is a cyclic number.

It is not a de Polignac number, because 666989 - 2⁸ = 666733 is a prime.

It is a super-2 number, since 2×666989² = 889748652242, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333494 + 333495.

It is an arithmetic number, because the mean of its divisors is an integer number (333495).

2⁶⁶⁶⁹⁸⁹ is an apocalyptic number.

It is an amenable number.

666989 is a deficient number, since it is larger than the sum of its proper divisors (1).

666989 is an equidigital number, since it uses as much as digits as its factorization.

666989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 139968, while the sum is 44.

The square root of 666989 is about 816.6939451227. The cubic root of 666989 is about 87.3721234103.

The spelling of 666989 in words is "six hundred sixty-six thousand, nine hundred eighty-nine".