Social security number usually refers to China's social security card number, also known as social security number or social insurance number. This number is used to identify an individual's unique identity in the social security system in China. Social security number is mainly used to record personal social insurance information, such as pension insurance, medical insurance, unemployment insurance, etc. **Structure of social security number:** 1. **Region code**: The first 6 digits indicate the region code. This is similar to the first 6 digits of the ID card number, indicating a specific administrative division. 2. **Date of birth**: The next 8 digits indicate the date of birth, in the format of YYYYMMDD. 3. **Sequence code**: After the date of birth, there is a set of sequence codes (usually 3 digits) used to distinguish people from the same region and date of birth. 4. **Check code**: The last digit is the check code, which is used to verify the validity of the number. **Example explanation:** Assuming the social security number is "12345619900101123X": - "123456" indicates your region (such as province, city, district). - "19900101" indicates your date of birth, January 1, 1990. - "123" is the sequence code. - "X" is the check code. It should be noted that there is no unified format for social security numbers across the country, and some cities may have their own special numbering rules. In addition, a person's social security card is usually bound to their ID number, so in many places the social security card number is your ID number. Be sure to protect your personal social security number and avoid leaking it to criminals to prevent potential risks to your personal information and finances.