Here is a learning support on the conventions for writing numbers in prose. This document has a big open field, and is in Microsoft Word, so it is at your–and more importantly, your students’–disposal; you can modify or adapt it to your needs.
If you find typos in this document, I would appreciate a notification. And, as always, if you find this material useful in your practice, I would be grateful to hear what you think of it. I seek your peer review.