668609 has 2 divisors, whose sum is σ = 668610. Its totient is φ = 668608.

The previous prime is 668599. The next prime is 668611. The reversal of 668609 is 906866.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 418609 + 250000 = 647^2 + 500^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-668609 is a prime.

Together with 668611, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (668699) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334304 + 334305.

It is an arithmetic number, because the mean of its divisors is an integer number (334305).

2⁶⁶⁸⁶⁰⁹ is an apocalyptic number.

It is an amenable number.

668609 is a deficient number, since it is larger than the sum of its proper divisors (1).

668609 is an equidigital number, since it uses as much as digits as its factorization.

668609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15552, while the sum is 35.

The square root of 668609 is about 817.6851472297. The cubic root of 668609 is about 87.4428034365.

The spelling of 668609 in words is "six hundred sixty-eight thousand, six hundred nine".