A standard industry format for number normalization. The E.164 format consists of a country code (1-3 digits) and a National Significant Number (12-14 digits) for a total of 15 digits. The National Significant Number consists in turn of a National Destination Number and a Subscriber Number (extension). For example, (425) 555-1212 ext. 3011 is represented in E.164 format as 42555512123011.