Some partial steps today, at least partially related. highest-common-factor was made a synonym of the greatest-common-divisor tag. The gcd ⇒ divisibility synonym has been removed. Unfortunately, when I created this synonym (Why did I do that? I was young and dumb then, I guess. Now, I'm older.)...

I propose a tag gcd-and-lcm to be created into which gcd, lcm, greatest- common-divisor etc. are mapped. On the one hand, the notion of GCD (and related) is relevant and wide-spread enough to merit a tag beyond the very general divisibility. On the other hand, the notions GCD and LCM are very ...