451

451 is the natural number that follows 450 and precedes 452. It is an odd composite number, the product of the primes 11 and 41. Its divisors are 1, 11, 41, and 451; thus it is a semiprime and square-free. In Roman numerals it is written as CDLI. In binary, 451 is 111000011.

Fahrenheit 451 refers to a famous 1953 dystopian novel by Ray Bradbury, in which a society burns books. The title signifies a temperature associated with paper ignition, a symbolic choice rather than a precise scientific fact. The book has been adapted into a 1966 film directed by François Truffaut.

In modern computing, HTTP status code 451, "Unavailable For Legal Reasons," is defined to be returned when access is blocked for legal reasons. It was introduced to standardize responses when governments or courts restrict content, and it appears in various standards and proposals related to web protocol handling.

Historically, the year AD 451 saw the Battle of the Catalaunian Plains, a major confrontation in which Roman general Flavius Aetius and Visigothic allies faced Attila the Hun. The engagement is often cited as a significant event in the late Roman era and the broader struggle between the Roman world and the Huns.