Yoruba is one of several major West-African languages including Ibo and Edo that have existed along the region's tropical belt for at least 4,000 years. It is spoken by approximately 30 million people. The language's influence is detectable among the African Diaspora in various places around the world including Brazil, Cuba and some Caribbean islands where Creoles with a decidedly West-African bent are spoken. There are several markedly different dialects that are mutually intelligible for the most part though these are gradually giving way to a single, standard, more modern form.
Counting higher than 10 in Yoruba is actually easy because it follows a predetermined formula. One to ten reads as follows, okan (or eni), eji, eta, erin, arun, efa, eje, ejo, esan, ewa. Din, with a nasal n, means less or short while le, with the e ending pronounced -ay means more. Now, with 20 being ogun, 19 becomes 20 less 1 or mokan din l'ogun (verbal shorthand for mokan din ni ogun). 21 reads mokan le l'ogun or 20 and 1. So...
16-merin din l'ogun (20 less 4) 18-meji din l'ogun (20 less 2) 23-meta le l'ogun (20 and 3)
25-marun le l'ogun (20 and 5)
The switch from le to din occurs after 15, 25, 35 etc. There are 5 easy exceptions to this formula; 11, 12, 13, 14 and 15 are mokanla, mejila, metala, merinla and marunla respectively. Why this is so, I know not.