I know my boy can write number "1" at age 2+. After all, he is good at scribbling any lines or sketching any shapes of his favor. But this year, he starts attending a formal class (not playschool anymore) and he is taught to trace (yeap, not write from the root) the numbers and alphabets progressively.
To help him learn better, I put up a number chart onto the wall of our bedroom. So every night, he can point and read the numbers which he can recognise. Also, he is very keen on writing with Fisher Price's "Doodle" drawing board... but we are freaked when he can write number "2" as well. We are pretty happy to learn about his progress and wish he can do better at his own pace.
Keep it up!!!