The structure and generation rules of social security numbers in different regions are different. Take the common social security number in my country as an example, it is the citizen identity number. The citizen identity number is a characteristic combination code, consisting of a 17-digit body code and a one-digit check code. The arrangement order from left to right is: a six-digit address code, an eight-digit date of birth code, a three-digit sequence code and a one-digit check code. The address code indicates the administrative division code of the county (city, banner, district) where the coded object is registered. The date of birth code indicates the year, month and day of the birth of the coded object, and no separator is used between the year, month and day codes. The sequence code indicates the sequence number assigned to people born in the same year, month and day within the area identified by the same address code. The odd numbers of the sequence code are assigned to males, and the even numbers are assigned to females. The check code is calculated based on the previous 17-digit code according to the ISO 7064:1983.MOD 11-2 check code. For example, a social security number is: 44030619800101001X. - 440306 is the address code, indicating Bao'an District, Shenzhen City, Guangdong Province. - 19800101 is the date of birth code, indicating birth on January 1, 1980. - 001 is the sequence code. - X is the check code. It should be noted that the insurance number used in social security business also has specific coding rules in different systems and scenarios, which is different from the citizen ID number. Here we mainly introduce the rules of the citizen ID number as an important part of the social security identification.