Short answer
HubSpot's KB: the default phone number field accepts numbers and common phone characters such as + - ( ) . x. When you set length restrictions, the country code is included in the count. In the updated editor, the field shows a country selector with the dialing code. For CRM-level formatting, see phone number property validation.
1. In the editor
A form in my demo portal: the phone field shows a country selector and dialing code.
