A bank account number is a unique identifier assigned to an individual's or business's account at a financial institution. This number is used to facilitate transactions, such as deposits and withdrawals, ensuring that funds are accurately directed to the correct account. It typically consists of a series of digits and may vary in length depending on the bank. When you open an account with a bank, you will receive a bank account number along with other details like the routing number. It is important to keep this number secure, as it can be used for unauthorized access to your funds if it falls into the wrong hands.