My son played this game for Android phones this weekend, and loved it! I thought it might be good for helping children with autism learn both numbers and other vocabulary, as it says the name of each number as you connect the line to it and shows a graphic and spoken name of the object made by connecting the lines. It seems very visually-structured, so I think it would be beneficial for children with autism, as visual processing is often an area of strength.
There is a free version of the app, as well as a paid version that has more puzzles. It may be available on other phones as well. You could do a search on your phone's app store for "Kids Connect the Dots."