Would this be the proper way to ask

"What is your telephone number?

Cad is uimhir telefón duit?

As I've mentioned, I've only been studying about 1 month, and I'm trying to understand the different ways that the personal pronouns are used.

Slán agus beannacht,
Faber MacMhaolain

Cad é an uimhir theileafóin atá agat?

1. For "Cad é", you may substitute "Cén".
2. For "theileafóin", you may also say "ghutháin". Many speakers will prefer this because it is a native Irish word rather than a borrowing. Whatever word you use, it must be in the genitive (i.e. "number of telephone"). Under no circumstances is "telefón" is a correct rendering of an Irish pronunciation of "telephone".
3. It may also be possible to use possessive pronoun "do" instead of the phrase "atá agat" (lit. "which is at you"). In that case, it would contract with "uimhir", i.e. "d'uimhir[*] theileafóin/ghutháin". But I would avoid this as it sounds much to "Englishy" to my ears.

[*] Pronounced "t'uimhir" in some dialects.

"Cad is uimhir theileafóin duit" is obviously based on "Cad is ainm duit" and is correct grammatically but no one says that. It suggests very ancient speech like "thee" and "thine" in English.

"Cén uimhir fóin atá agat?" or "Cad é d'uimhir theileafóin, le do thoil?" would be more common. In the case of "uimhir fóin" the word "fón" seems to be regarded as foreign and the "f" is not lenited. [lenition and f don't seem to get on too well. I wonder is that mentioned in the grammars?]

I agree with Domhnaillín that guthán and uimhir ghutháin are commonly used and preferred by many. "Fón póca" however is the Irish for cellphone which in Ireland is a mobile.

quote:

"Cad is uimhir theileafóin duit" is obviously based on "Cad is ainm duit" and is correct grammatically but no one says that. It suggests very ancient speech like "thee" and "thine" in English.

Isn't this a difference of inalienable vs. alienable possession? A phone number, like a phone, is something you may have at a given time or may not, whereas a name follows you throughout your life.

Go raibh maith agat.

FaberM

How is "cad é (an)" different from "cén"? I thought the former meant "what" (i.e. "what colour...?") and the latter meant "which" (i.e. "which house is yours?" pointing out a few houses), but it seems they are interchangeable. Are there any rules when one should be used and not the other?