Can I have your phone number?
'Numero' = NU-me-ro, stress on first syllable. 'Telefono' = te-LE-fo-no, stress on second syllable.
Use this at the end of a positive first meeting to continue the friendship. Italians readily exchange numbers with new acquaintances and expect to be contacted. Not asking for a number can be seen as a sign of indifference after a good conversation.
'Posso' (I can/may) + infinitive is the standard way to make polite requests. 'Avere' here means 'to have/get'. The full thing requested is 'numero di telefono' — in informal speech often shortened to just 'numero'.
Mi dai il tuo numero?
Will you give me your number?
More direct and informal — implies more confidence in the interaction
Ti aggiungo su WhatsApp?
Shall I add you on WhatsApp?
WhatsApp is the dominant messaging platform in Italy — very modern
Come ti trovo su Instagram?
How do I find you on Instagram?
Social media alternative for younger generations
WhatsApp is used by virtually all Italian adults for personal communication. Exchanging numbers in Italy almost always means connecting on WhatsApp. Italian communication culture is warm and spontaneous — receiving a message from a new acquaintance the same day is completely normal and welcome.