PZN-Validator Provides a isValidPZN() Method, which checks if the supplied number is a valid PZN and returns true or false If you're reading this, you're probalby know what a PZN is but you can find more Information about PZNs here: https://de.wikipedia.org/wiki/Pharmazentralnummer http://pzn8.de/de/home/informationsblaetter