Biggest number in computer ever

Question

Just asked by my 5 year old kid: what is the biggest number in the computer?

We are not talking about max number for a specific data types, but the biggest number that a

Answer 1

Errr this is a five year old?

How about something along the lines of: "I'd love to tell you but the number is so big and would take so long to say, I'd die before I finished telling you".