Return this object's normalised phone number.
Typical normalisations:
- 1-800-123-4567 → 18001234567
1-800-123-4567
18001234567
- +1-800-123-4567 → +18001234567
+1-800-123-4567
+18001234567
- +1-800-123-4567P123 → +18001234567P123
+1-800-123-4567P123
+18001234567P123
the normalised form of number
number
0.6.0