SIREN codes are given to French businesses and nonprofit associations, SIRET codes to their establishments and facilities. SIREN codes are maintained by the French INSEE. This is French-specific, and will not change during the lifetime of the business.
SIREN codes have 9 digits. The first 8 digits are the business reference, the last one is a key created with the 8 previous ones to control the validity of the code. French public organizations have 1 or 2 as first digit.
The control key is used to check the validity of the code and uses the Luhn algorithm.