An integer is said to be nine-separable if it can be represented as the product of two positive integers that differ by nine. (For example, since $$22=2\times 11$$, $$22$$ is nine-separable.) Similarly, an integer is said to be eighteen-separable if it can be represented as the product of two positive integers that differ by $$18$$. What is the sum of all positive integers that are both nine-separable and eighteen-separable?