Changzhou ID card number format: 320400ABCDEFGHIJKL, the length is 18 digits, the first 17 digits are all digits, and 18 digits are mostly digits, with a few letters "X". Among them, 320400 is the area code of Changzhou (the administrative district code where the registered permanent residence is located).

ABCD is the year of birth, EF is the month of birth, GH is the date of birth, IJK is the sequence code (in the same area, the sequence number compiled for people born on the same day), K is the gender code (singular male, even female), and L is the last check code (calculated according to the unified formula, the calculation result is 0- 10, and x is used instead of 10).