255

255 is the natural number that follows 254 and precedes 256. In mathematics, it equals 2^8 − 1 and has prime factorization 3 × 5 × 17. It is not a prime number.

In numeral systems, 255 is represented as 11111111 in binary, FF in hexadecimal, and 377 in octal. Its binary form makes it a convenient representative of a full byte, since all eight bits are set.

A common usage of 255 is as the maximum value of an unsigned 8-bit integer. This makes 255 a standard color channel maximum in 24-bit color, where each of the red, green, and blue channels ranges from 0 to 255. The same 0–255 range applies to many digital storage and processing contexts.

In networking, each octet in IPv4 addresses uses the 0–255 range; the address 255.255.255.255 represents the local broadcast address on a network.

In character encoding, decimal 255 maps to the character ÿ in ISO/IEC 8859-1 (Latin-1) and to the Unicode code point U+00FF. This value is commonly encountered when interpreting extended ASCII or Unicode data.

In computing more generally, 255 is often used as a bitmask (0xFF), representing a byte with all bits set. This makes it a frequent reference point in discussions of memory, data width, and low-level bitwise operations.