EDIT (2014-03-08): I’ve done a complete revision of the design and features. Have a look!
I wrote this little app in my spartan basement suite apartment in Vancouver in autumn 2013.
It’s a tool to help people who are learning Japanese. Large numbers in Japanese are a pain for English-speakers (and vice-versa) because they’re grouped in 4s, not 3s — but only after you get above 1,000.
Compare this to our units of thousand, million and billion.
Since I kept getting these wrong, I wrote an app to help. You can experiment by generating random numbers or typing in your own and seeing what they look like in Japanese.