Mentat Wiki: "Number Shape System"
Read this brief article, which shows you how you can remember numbers by associating them with shapes that look like numbers. Take a moment to follow the link to Wikimedia Commons at the end of the page. There, you will find many more examples of shapes that can be used to remember numbers.
The number shape system is a method of replacing hard to remember and abstract numbers with an image which is easy to remember. As an example the number one is replaced with an image which is similar in shape to the number '1', such as a pen, pencil or arrow. The other numbers can similarly be replaced and the following sequence is one suggestion for the numbers 0 to 9: tire, candle, swan, heart, yacht, hook, an elephant's trunk, axe, hour glass, and tennis racket.
As an example, to remember that the number of a house you must visit is number seven, visualize the house door and imagine you are breaking into it with the axe.
The number shape system can also be used as a PegSystem giving you ten pegs on which to hang useful facts. In this case link the ten items to remember with each of the number shape images. You can now recall the items in any order and at random by visualizing the number shape for the item you wish to recover and remembering the link.
Wikimedia Commons has a category of shapes for number shape system here.