The IMO number is a unique identification reference of 7 digits, prefixed by ‘IMO’ that is given to a vessel as a permanent number for identification purposes.
The IMO number is assigned by the International Maritime Organisation (IMO) to propelled, sea-going merchant ships of 100 gross tons (GT) additional information can be accessed here .
The IMO number remains unchanged throughout the vessel’s lifetime, even if the ship’s name, ownership, or flag state changes. Vessel IMO numbers can be looked at on Ships List with Details and Live Maps