What is the Mavis Beacon Teaches Typing Deluxe 17 free serial number?

Unfortunately, the software that you can download for Mavis Beacon Teaches Typing is not actually free. It is just a demo that you can use temporarily, and after that you have to provide a serial number to use it. Many companies distribute free-to-try versions like this in order to let people understand what they are getting and convince them to buy it.

Last I checked though (2017), this software can be purchased for about ten dollars on Amazon (actually version 18), and an older version (version 16) is available for $6. That's not free, but it is a very good price.