Unique product numbers, is that possible?

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-- HikaShop version -- : 3.4.0
-- Joomla version -- : 3.8.7
-- PHP version -- : 7.1
-- Browser(s) name and version -- : Firefox 59.02
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I'm going to sell digital products. Each product requires a unique product number. Clients will have to submit their product number + email address for support and updates. The email address is not a problem, but I have no idea how I can generate unique numbers for a product.

The number should be created when the client buys his product. Where and how is not important. If , for example, the product numbers shows up on the invoice, that's good enough for me.

Is this possible? And if yes, how do I do that?