The number 451 is significant because it represents the temperature at which paper catches on fire and burns, which is instrumental to the central concept of the story. In Bradbury's dystopia, the authoritarian government censors literature and establishes the fireman institution to specifically burn books, libraries, and the homes of dissidents. Firemen are armed with kerosene fuel tanks and wield deadly flamethrowers that spew fire and create a spectacle.
The story's protagonist, Montag, is a disgruntled fireman who has become jaded about his occupation and entertains the idea of reading books. The number 451 is inscribed on his fireman helmet, uniform, and equipment. These numerals symbolically represent Montag's destructive occupation and the war being waged against authors and intellectuals throughout society.
When Montag first meets Clarisse, he takes offense at her cavalier demeanor and asks if she has any respect. Montag proceeds to tap the 451 numerals stitched on his uniform and asks Clarisse if the numbers mean anything to her. Montag's gesture and comment indicate that the numerals 451 are well known throughout society and represent the oppressive, hostile government institution. The numerals are meant to intimidate civilians and remind them of the government's authority. In addition to the 451 numerals, the salamander and phoenix are other significant signals that represent the destructive fireman institution.
Glad to Help!
stay blessed and stay up!