What does the author indicate about the importance of the number 451 and the fireman's job?

Ray Bradbury tells us that 451 degrees Fahrenheit is the temperature at which paper burns.

As far as the importance of the fireman's job, it is to keep people happy.  Bradbury tells us that books made people think too much.  When people would think too much, they would become unhappy.  So the society started to have the elaborate television systems (the parlor walls) and violence and fast cars and such so that they could not have to think.

The fireman's role in this is to make sure that no books can survive to threaten this ignorance.