The official phone number of a person, place, object, company, or other entity is the main or preferred telephone number used to establish contact with that entity. Telephone numbers should always begin with a + sign followed by the international dialing code; this is followed by any further area code(s) according to national or regional requirements. Blocks of numerals should be separated by spaces rather than hyphens (-) or dots (.). The spacing of blocks varies according to the length of the number and national custom. Alphabetical letters should be converted to their corresponding numeric digits. Digits which are omitted in international calls may be enclosed in parentheses; otherwise no parentheses should be used. Example (showing North American spacing): +1 555 555 5555

The number supplies the main or preferred route to the entity itself. A primary telephone contact for a property can instead identify whichever responsible party is most relevant to inquiries about that property.

The required international prefix and spacing describe how the contact number is recorded. Optional digits omitted for international calls may use parentheses under the stated rule; ordinary area-code blocks do not receive parentheses solely for visual grouping.