The numbers at the end of a runway aren't just there to help pilots see where they're supposed to land. They actually mean something important: the runway's degree from magnetic north. This video from Atlas Obscura explains.
The video is only about a minute long, so it's worth a watch, even though the cat's out of the bag here -- each runway number represents its degree, labelled one through 36 -- from magnetic north, rounded down to the lowest two digit number. So runway 12, for example, is 120 degrees from magnetic north, and runway 36 is, well, 360 degrees from magnetic north, and it means you're pointed directly north.
That all said, magnetic north is known to shift, and move great distances over the years, which then makes all of those numbers completely wrong when it does. When it's necessary, that means a runway number change, which also means repainting the number on the runway. It's not the most practical piece of information, but it's definitely something you can use the next time you take a flight and come in for a landing or take off from an airport to get a little sense of your relationship with the planet.
Runway Numbers | Everything Decoded [Atlas Obscura (YouTube)]