An identification number (also known as a registration number) is an alphanumeric value assigned to a character, object, or thing that needs to be tracked through a registry system. Identification numbers are commonly depicted with a hashtag.

Examples

• Numbers associated with fictional groups of species in games such as Pokémon.
• Number on an ear tag (most likely). See numbered tag
• Number on a prison uniform.
• License plate registration number (Might not make sense to tag as an id number though).