Along with the other comments on UDID, IMEI and MAC, I’d just like to point out that phones don’t have phone numbers.
On land lines, the number is assigned to the line that goes to your house from the local operations center; on mobile phones, the number is linked by your carrier to THEIR SIM card that you stick in your phone.
eSIM almost gets there; instead of a physical card linked to the phone number, all the logic and secrets are stored in a secure enclave on your phone and THAT is linked to the number, which is in a directory managed by your carrier. It’s linked to the phone itself because of the phone’s IMEI.