555-7009-073 is part of a seven-digit phone number in the North American Numbering Plan (NANP). The first three digits, 555, identify the locality of the number, which is usually a city or county, but can be a special code. The next three digits, 7009, identify an exchange, which is a specific telephone switching system in the locality. The last four digits, 073, identify a unique phone number within the exchange.