I think I was most impressed by Annabeth Gish's ability to remember all the numerology stuff. It's complicated and interesting and this really makes for a good episode that is totally silly, very well acted and puts characters in situations that they wouldn't normally be.
Burt Reynolds is fine as the game player and dealer of advice that makes little sense. The scene between him, Scully and Reyes is so X Files - very funny and then suddenly turns to have a reason that's far from fun.
I couldn't quite work out whether the serial killer was using numbers or whether they were in some way choosing him. But hey, he liked killing people, so I'm not going to go into his motives that much.
The music was very different in this episode too, as were some of the settings. I almost found the music annoying in parts, but I think it really did add something to the flavour of the whole thing.
Another welcome 'lighter' addition to season 9 (if stories about serial killers can be light!)