Earlier quoted context omitted.
You mean like those guaranteed-always-compresses-by-at-least-one-bit algorithm patents gzip page made fun of? In your case, doing prime factoring is where the cost would be, wouldn't it?
Yes, but the point is to look for different representations, not necessarily use this specific one.
Yes, sometimes a neat trick like the one in the article of replacing one multiplication with substraction appears, but that is not as universal.