su teléfono OR
tu teléfono
El telefono
teléfono - Spanish
Telefono is Spanish for Telephone.
número de teléfono
You can say "No sé donde está tu teléfono."
Hablas mucho por telefono.
The way that you would say what is the best telephone number to contact you at in Spanish would be cad é an uimhir theileafóin is fearr chun teagmháil a dhéanamh leat ag. If you just wanted to ask what is your telephone number you would say cad é d'uimhir ghutháin.
Quieres que te compro un telefono (movil)? Do you want me to get (buy) you a (mobile) telephone?
un teléfono celular ...
* In Portuguese = cabine telefônica * In Spanish = cabina telefónica
For instance if your number was: 123-4567 it would look like 1-23-45-67 in spanish.
Google translator states it as "hablando por teléfono"