What is the best way to write a phone number? Are there any studies in this regard?
I personally consider two factors:
The first example I think is more legible, but perhaps not understandable for those who do not have the proper familiarity with the phone.
+39 340 12 34 xxx
I personally use spacing every 2-3 digits because I think it is more readable, especially for dyslexics. But I'm not sure the best way.