Each American born today must be issued a social security number. This been the practice since 1936. By 2009, 420 million social security numbers had been issued, according to the Social Security Administration (SSA).
The First Digit Set
The first three digits of a social security number stand indicate the location of the birth. Each area has a different code, like and area code on a telephone number. The SSA says that the area numbers are based on the mailing address of the birth certificate.
The Second Digit Set
This is the group number. Inside each area, the two digit group number serves as further separation, dividing the people into 100 groups (for the numbers 00 through 99). They are not assigned consecutively.
The Third Digit Set
Also called the serial group, these numbers are four digits are assigned consecutively. They range from the numbers 0001 to 9999.
The two digit group number does not signify the race of the person bearing the number. They are issued randomly within each area.
The SSA assures the public that there is no need to repeat social security numbers. There are enough number combinations to identify several more generations of Americans without reusing numbers.