Social security number usually refers to China's social security number, also known as social security registration number. It consists of 18 digits, and the specific structure is as follows: 1. **Region code (first 6 digits)**: This part represents the administrative region where the insured person is located, and is uniformly assigned by China's social security system. 2. **Date of birth (7-14 digits)**: This part contains the insured person's date of birth, in the format of YYYYMMDD, for example, January 1, 1990 is represented as 19900101. 3. **Sequence code (15-17 digits)**: These three digits are used to distinguish between people born on the same day and insured in the same place. Generally speaking, the sequence code for men is an odd number, and the sequence code for women is an even number. 4. **Check code (18th digit)**: This digit is obtained through certain calculation rules and is used to verify the validity of the social security number. ### Interpretation of the example social security number Assume that there is a social security number: ``11 123456 19900101 001 5`` - **Region code**: `11 123456` represents a specific region (such as Beijing). - **Date of birth**: `19900101` indicates that the insured person was born on January 1, 1990. - **Sequence code**: `001` is the first insured person registered in the region with that date of birth. - **Verification code**: `5` is the calculated verification code. ### Generation rules Social security numbers cannot be generated arbitrarily. They must be applied for through formal channels (such as the Human Resources and Social Security Bureau) and allocated by the relevant system. When an individual applies for social security, a unique social security number will be generated based on their identity information, date of birth and the coding rules of the relevant region. Please note that the above is only an example of the structure of a social security number. The format and generation rules of the actual number may vary slightly from region to region. If you need detailed information, it is recommended to consult the relevant information of the local social security bureau.