Too funny because this one came right after "how many apples do the horses eat on average?" :D
The excrements of a horse are named "Pferdeäpfel" in German. Sounds like a limit of defecation for horses. Nå vite jeg, det heter hestepærer i norsk.
7 epler per hest. Is not accepted?
Numbers below 13 are to be written out in running text. There are exceptions, such as dates, times and measurements, but this is not one of them.
Besides, you're here to learn Norwegian, not how to write the numeral "7". :)