"Thirteen, fifteen and sixteen are numbers."

Translation: Tretten, femten og seksten er tal.

[bondybondbond]

not possible to say "numre" here?

[Xneb]

nummer is used for things like telephone numbers and house numbers and other systematic things and don't contain only numbers, tal is used for the individual numbers that one can count

[KasperFeld]

Thirteen, fifteen and sixteen er "tal" definitely, but they are certainly "numre" as well. I know someone who lives in nummer femten.

[km1]

tal means digits

[habitist]

@Km1, not entirely. Digits are each unit of a number. fx, 69 is one "tal", but it is two "digits".
I believe the correct translation for digits, is "cifre"

[FabianRxse]

What is the plural of tal and why is it not used here?

[S851648]

The plural of "tal" is "tal".