Easy and adorable cake decorating idea! Fill a cookie cutter with sprinkles, it doesn't have to be a number. Just pick it up! (You can make a shape that's "faded" at the edges by filling the cookie cutter up to the top and lifting it up quick.
Place number on cake, sprinkle with sprinkles. Okay, this was a cute idea, but time consuming, trying to the sprinkles onto the cake. And the number stuck so I had to refrost the bare portion. Cake was a huge hit though!