The Norwegian birth number (ID) is an 11-digit personal identifier. Everyone in the National Register has a birth number. If you are not born in Norway, you will usually be given the D number (a temporary ID number) which will become your permanent ID number when the necessary criteria is met.
The social security number you get as a foreigner depends on your residence permit and how long you plan to stay in Norway. There are two cases in which you may be entitled to a D number. In the first case, if you intend to stay in Norway for less than 6 months. The second situation is that you intend to stay in Norway for more than 6 months, but do not meet the criteria for being assigned a birth number.
At Tecla, we have experience with this process and can help you navigate through this.