Visual mnemonics are a type of mnemonic that work by associating an image with characters or objects whose name sounds like the item that has to be memorized.
Digits can be memorized by their shapes, so that: 0 -looks like an egg, or a ball; 1 -a pencil, or a candle; 2 -a duck, or a swan; 3 -an ear; a pair of pouted lips.
4 -a sail, a yacht; 5 -a key; 6 -a comet; 7 -a knee; 8 -a snowman, or a pair of glasses; 9 -an apostrophe, or comma.