Ahref has published an interesting study that shows how many other keywords a single page can rank for in Google. Typically, SEOs tend to try to optimize each individual page for its own keyword phrase.
But the study showed that the average number one ranking page will also rank in the top 10 results for about 1,000 other relevant keywords. The median value is less than half that, with around 400 relevant keywords.
If you break it down by high-volume keywords, the study said “ranking for 2–3 keywords with over 1,000 searches per month is quite common. While ranking for more than one 10k+ keyword with a single page is very rare.”
Finally, Ahrefs broke it down to see how many keywords a page ranks for are unique to the point where they don’t have even a single common keyword with the rest of the group. It showed that the number of unique keywords is extremely low.
You can read the full study over here.