A number-to-words tool that grew from one Android app to four platforms

Writing an amount in words is mandatory on cheques and invoices, and it is the step people get wrong most often — French has irregular forms like soixante-dix and quatre-vingts plus agreement rules on cent and vingt, and Arabic adds gender and case agreement. Getting it wrong means a rejected cheque or a reissued invoice.

We shipped a single-purpose Android app in 2017 that did one thing correctly: turn a figure into a correctly written amount. It spread by word of mouth among accountants, businesses and administrations, and now runs on Android, iOS, web and Windows, writing amounts in French, Arabic and English.