Learn Swedish: Vilket är numret?

In Swedish, when you ask "what" to find out a specific identifier like a number, address, or date, you usually use the word for "which" (vilken/vilket/vilka). You are essentially asking which number it is out of all possible numbers, so vilket is used instead of vad.

How do I know whether to use vilken or vilket?

It depends on the gender of the noun you are asking about! The word for "number" is an ett word (ett nummer). Because of this, you must use the ett form of the question word, which is vilket. If you were asking about an en word, like an address (en adress), you would use vilken (Vilken är adressen?).

Why is "the number" spelled numret and not "nummeret"?

The base word is ett nummer. Normally, to say "the" for an ett word, you simply add -et to the end. However, when a noun ends in -er, it usually drops the final e before adding the suffix so it is easier to pronounce. So, nummer + et becomes numret.

Would a Swedish speaker say this to ask for a phone number?