What is the default for U.S. citizens over the age of 1 with an unknown social security number?

The default social security number for U.S. citizens over the age of 1 with an unknown social security number is the sequence of all sevens, which is 777-77-7777. This number is often used in systems to signify that the actual social security number is not available or unknown, serving as a placeholder.

This convention helps to prevent confusion in data management and processing, allowing systems to easily identify records that are missing this critical piece of information without inadvertently assigning a valid social security number. The other sequences—such as all nines or all zeros—are typically reserved for specific purposes or categories and do not serve the same function as the all sevens default.