It's unique, but it encodes your birthday and sex.
There's only 500 numbers it could be, assuming someone knows those other things about you.
In any case, there are alternative systems for authorisation.
There's only 500 numbers it could be, assuming someone knows those other things about you.
In any case, there are alternative systems for authorisation.
It's the same in Sweden: YYYY-MM-DD-XXXX is the format for a personnummer, double the population of Denmark and there are no collisions.
edit: I was wrong. Wikipedia says, “The first digit of the sequence number encodes the century of birth (so that centenarians are distinguished from infants)”.
It also says “the last digit of the sequence number is odd for males and even for females”. What a strange system. Essentially the last three digits are two different sequences made to look like one.
Thanks for correcting it :)