Convert Numbers into English text (521 to Five hundreds twenty one), this one called (SpellNumber) I found online.

And (Num2ArText) that will do the same but in Arabic language , (as 500 to خمسمائة). This is much harder by the way.
This Excel function can take other parameters other than the number if you want to customize it. It will also enable you to add the unit you want.
The only catch is that you need to copythe User-Defined-Functions into your file and enable macros.

Download from XLFxs.com

You can can also check the online version for Arabic language here