The UPC Number is a very valuable number and allows retailers that are using multiple systems to efficiently communicate. For example many retailers use UPC for the scanning label for the point of sales systems. Retailers will also use UPC to feed their products to Amazon or other 3rd party systems.
In the Specialty Toys Network program it gets used by retailers in their match-up criteria with their POS to populate their site plus it is a requirement in product search feeds like GoogleBase or Bing.
(numbers only, no spaces, dashes, or alpha characters)