Be aware of the inherent assumptions here - most numbers listed/quoted these days are 10 digits, and in fact a good old 7-digit number is often inadequate, as it is becoming increasingly harder to guess the area code. I regularly encounter phone numbers with a half-dozen area codes, all of which are considered "local".

In addition to this, the leading "1" is regularly but unnecessarily given.

If we were to consider international numbers, then there really is no good way to write a regex to extract it.