405

405 is the natural number that comes after 404 and before 406. It is an odd composite number with several notable mathematical properties.

In mathematics, 405 factors as 3^4 × 5. Its positive divisors are 1, 3, 5, 9, 15, 27, 45, 81, 135, and 405, for a total of 10 divisors. The sum of its divisors is 726. The number is divisible by the sum of its digits (4 + 0 + 5 = 9), making 405 a Harshad number in base 10. It is also a multiple of 45.

In computing, 405 is used as the HTTP status code 405, meaning Method Not Allowed. This response indicates that the server recognizes the request method but the target resource does not support it. The response typically includes an Allow header listing the permitted methods for the resource.

In telecommunications, 405 is the area code for central Oklahoma, including Oklahoma City and surrounding areas. Area code 405 is one of several codes serving the region and has seen overlays to accommodate growth.

In broadcasting history, the term 405-line refers to an early analog television standard with 405 vertical lines of resolution. Implemented in the United Kingdom in the 1930s, it was widely used into the 1950s–1960s and gradually replaced by higher-definition systems in subsequent decades.

Throughout calendar use, 405 can denote the year 405 in the Common Era, a point in late antiquity. The number appears in various historical and numerical contexts as a reference point or identifier.