Number One is a large white numeral shaped like a "1", living in Mainframe. Judging by his outfit he works for intelligence on behalf of the CPU defense force. He is one of the few numerals refered to with the title 'number' before his name, it may be a title for his job.
Without his expertise it would be nearly impossible for everyone else to give an accurate prediction in these kinds of situations. Number One was seen explaining to Dot that the city's Core was now inside a corrupted Game Cube, win or lose if the Cube leaves, the stolen energy would dissipate, destroying Mainframe in the process. (Bad Bob)
The Command.com of the damaged system in the episode icons was also the number one numeral.
- Number One's voice sounds like Sean Connery.
- He is a reference to Commander William T. Riker from Star Trek: The Next Generation, commonly referred to by his captain as "Number One".