440

440 is a natural number that follows 439 and precedes 441. In mathematics, it is an even composite number with prime factorization 2^3 × 5 × 11, and it has 16 positive divisors. In Roman numerals, it is CDXL. In binary it is 110111000; in octal 670; in hexadecimal 1B8.

In music, 440 refers to the standard pitch A above middle C, commonly designated A440. This concert pitch serves as a reference for tuning instruments and is widely used by orchestras and ensembles, though some groups prefer alternative tunings such as 442 Hz or 439.5 Hz.

In geography and communications, 440 is the North American area code for parts of Northeast Ohio, including Cleveland's western suburbs. It was introduced in the late 1990s as a split from area code 216.

In materials science, 440 denotes a family of stainless steel grades (for example 440A, 440B, 440C) known for high hardness and wear resistance; 440C, with high carbon content, is commonly used for cutlery and surgical instruments.

In other contexts, 440 may appear as a year in the Common Era (AD 440) or before the Common Era (440 BC), with various historical events depending on region.