My DS is 25 months and has just decided he's interested in numbers. I wouldn't say we ever talked about numbers very much but he woke up the other day with the ability to count objects up to four. Today, he is 'reading', or recognizing, the printed numbers 2 and 8. It really beats me, especially since he's been such a late talker--he only really started to talk a couple of weeks ago. Number words weren't even part of his vocab in imitation of us before this.
Just like puzzles, once he decided at 14 months they were interesting, that was it. Now, a 24 piece puzzle is only a minor challenge the first few times he works it and then it's too easy. But there are so many things other kids can do that he's been slow on. I guess some stuff he just doesn't give a rip about right now, and that stuff that he does, commands 100% of his focus.