A Social Security number is a unique nine-digit identification number issued by the federal government to track individual earnings histories, tax obligations, and social benefit eligibility, and it is entirely distinct from a bank account. It functions strictly as a personal identifier rather than a financial repository, meaning money cannot be deposited directly into a Social Security number. While financial institutions require your Social Security number to verify your identity and report interest income for tax purposes when opening a bank account, the number itself holds no banking functions, balances, or routing properties.