High Quality Content by WIKIPEDIA articles In the United States, a Social Security number (SSN) is a nine-digit number issued to U.S. citizens, permanent residents, and temporary (working) residents under section 205(c)(2) of the Social Security Act, codified as 42 U.S.C. 405(c)(2). The number is issued to an individual by the Social Security Administration, an independent agency of the United States government. Its primary purpose is to track...