Here's the info from the Social Security Administration: The digits in the Social Security number allow for the orderly assignment of numbers. The number is divided into three parts: the area, group and serial numbers.The first three (3) digits (area) of a person's social security number are determined by the ZIP Code of the mailing address shown on the application for a social security number.Within each area, the group number (middle two (2) digits) range from 01 to 99 but are not assigned in consecutive order.he number is divided into three parts: the area, group a â¦ nd serial numbers. The first three (3) digits (area) of a person's social security number are determined by the ZIP Code of the mailing address shown on the application for a social security number.