There's this thing called the IBM Information Center. It has this section
called "Database". Expand that and select "Reference", then expand "SQL
Reference". Select Built-in Functions. Then look at Scalar functions.
What you then want depends on whether or not you want leading zeros. Be
careful. Some will return those and some won't. One begins with CH and
one begins with DI.
Here's a good place to start
Combine the above with LIKE and you should have what you want.