The rules for generating bank account numbers vary by country, bank, and account type. The following are common rules and examples for reference： --- ###1. International bank account number (IBAN) IBAN (International Bank Account Number) is an internationally standardized account format that contains the country code, check digit, and basic bank account number (BBAN). **Format rules**： `Country code (2 letters) + check digit (2 digits) + bank code (usually 4-6 digits) + branch code (optional) + account number (remaining digits)` **example**： 1. **Germany**: `DE89 3704 0044 0532 0130 00` -'DE`: Germany -`89`: parity bit -`37040044': Bank code (Commerzbank) -`0532013000': account number 2. **United Kingdom**: 'GB29 NWBK 6016 1331 9268 19` -`GB`: United Kingdom -`29`: parity bit -`NWBK`: Bank code (NatWest) -`601613 31926819': branch code + account number 3. **France**: 'FR14 2004 1010 0505 0001 3M02 606` -`FR`: France -`14`: parity bit -`20041 01005 05000 13M02 606': bank code, branch code, account number, etc. **Verification rules**： The IBAN parity bit is verified by the **MOD 97 algorithm**. After converting the account number to a number, modulo 97 is taken. If the result is 1, it is valid. --- ###2. Bank of China account number Chinese personal accounts are usually **19 digits**, and corporate accounts may be 17 digits. The rules are customized by each bank. The common structure is as follows： **example**：`6228 4801 2345 6789 123` -**The first 6 digits**: The identity of the issuing bank (for example, 622848 is Agricultural Bank of China) -**Middle 7-10 digits**: Area code + branch code (for example, `01' may represent a branch in a certain province or city) -**Last digit **: sequence number + verification code (some banks may include Luhn algorithm verification) **Note**: There is no unified public verification rule for Chinese account numbers, and some banks may use the last digit as the check digit. --- ###3. U.S. bank account number U.S. account number (Checking Account) is usually **9-12 digits**, the rules are customized by the bank, the common structure is as follows： **Example**:`021000021 9876543210` -**The first 4 digits**: Bank routing number (routing number, such as `0210'represents a bank) -**Middle 4 digits**: branch code (optional) -**Remaining digits**: unique account identifier **Verification rules**: Some bank routing numbers are verified using the **MOD 10 algorithm**. --- ###4. Other rules 1. **Luhn algorithm**： It is used to verify the validity of the card number (such as a credit card), but it is rarely used for bank account numbers. **Step **: The numbers are from right to left, the even digits are multiplied by 2 and then added. If the sum can be divisible by 10, it is valid. 2. **Custom check code**： Some banks add a 1-2-digit verification code at the end of the account number, which is generated by an internal algorithm. --- ###5. Precautions 1. **Non-disclosure rules**: Most banks do not disclose the details of account number generation. The above is only the general logic. 2. **Safety tips**: Do not disclose the real bank account number, the examples are fictitious. 3. **Practical application**: You need to follow local financial regulations when developing tests, or use the test account provided by the bank. If you need detailed rules for a specific country/bank, it is recommended to check the official documentation or contact a financial institution for confirmation.