How to get someone's phone number

In order to get someone's phone number you must know:

-How to ask "What is your phone number?"

-The numbers in general.  

To ask someone for their number you cuål es tu (su if adult) numero de teléfono? "This means what is your phone number?"

The numbers are 1-9 so the person's answer will be in uno, dos, tres, cuatro, cinco, seis, siete, ocho, or nueve. The numbers will never go 10 or higher.
After getting help for a homework a student ask for his friends number.