The rules for the generation of bank account numbers are usually formulated by central banks or financial institutions of various countries, and the rules of different countries and banks vary greatly. The following are some common examples and general rules, but it should be noted that this information** cannot be used for actual account opening or verification**, and is for learning reference only： --- ###1. Examples of common international account number rules 1. **IBAN (international bank account number)** -** Format **: Country code (2 letters) + verification code (2 numbers) + bank code (usually 4 characters) + branch code (usually 4 characters) + account number (remaining part) -**Example**: `GB29 NWBK 6016 1331 9268 19` (United Kingdom) -`GB`: country code -`29`: Check code (generated by algorithm) -`NWBK`: Bank code (such as HSBC) -`6016 1331': branch and account information 2. **US account number** -Usually 8-12 digits, there are no uniform rules, and it is customized by the bank. May contain： -The first 4 digits: bank code (such as Chase's `0210`) -Middle bit: branch code -End: customer's unique account number --- ###2. Bank of China account rules (take debit card as an example) 1. **19-digit account number structure** (e.g.: `6222 1234 5678 9012 345`) -**The first 6 digits**: The identity of the issuing bank (for example, `622202' is ICBC) -**Middle 7-9 digits**: Area code + outlet code -**8-10 digits at the end**: The customer's unique account number -**Check code**: Some banks verify the last digit through the Luhn algorithm (common in credit cards). 2. **Public account** - Usually starts with `1`, the number of digits may be different (such as 18 digits), and contains information such as bank, branch, account type, etc. --- ###3. General generation logic (technical reference) 1. **Verification algorithm** (such as Luhn algorithm) -Used to prevent input errors, such as the last digit of the credit card number is calculated from the first few digits. -**Example**： ```python def luhn_checksum(card_number): digits = [int(x) for x in str(card_number)] odd_digits = digits[-1::-2] even_digits = digits[-2::-2] checksum = sum(odd_digits) + sum(sum(divmod(2*d, 10)) for d in even_digits) return checksum % 10 == 0 ``` 2. **Internal bank rules** -The account number may be embedded: account opening date, customer ID hash value, product type code, etc. --- ###4. Important reminders -**It is strictly prohibited to simulate a real account**: Generating or analyzing a real account may involve legal risks. -**Test purpose**: The test number provided by the bank (such as PayPal's `4111 1111 1111`) can be used during development. -**Privacy protection**: Do not disclose your real account information. If you need to learn more about the rules of a country/bank, it is recommended to check its official documentation or contact customer service.