Resources to drill multiplication facts up to 20x20?

Hi all! I am a high school math teacher and I would like to find a tool, preferably an app for iOS, that allows interested students (and honestly myself) to memorize the multiplication table up to 20x20. Most of the resources that I found only go up to 12x12, but I have had some students ask for an app that allows them to go higher. I was thinking of Quizlet, but they have added a bunch of annoying ads and the app just doesn't work as well as it used to. Do you all have any recommendations? Thanks in advance!