256

256 is a natural number that comes after 255 and before 257. In mathematics, it is 2 to the 8th power (2^8), and it is both a square (16^2) and a fourth power (4^4). Its prime factorization is 2^8, so it is a power of two. The sum of its divisors equals 511. It is not a prime or a perfect number.

In numeral representations, 256 is written as 256 in base 10, 100000000 in binary, 0x100 in hexadecimal, and 0400 in octal (or 400 in plain octal). This reflects its role as 2^8 and its place as a boundary between 0–255 for eight-bit quantities.

Computing and digital systems commonly use 256 as a fundamental value. An 8-bit byte can store 256 distinct values, from 0 to 255. Historically, 256-color graphics use an 8-bit indexed color palette, providing 256 possible colors. Many data structures and memory systems employ 256 as a block or alignment size because powers of two simplify addressing and storage calculations.

In character encoding, 256 code points are defined in legacy single-byte encodings such as ISO/IEC 8859-1, which laid groundwork for interpreting 8-bit text. In Unicode, the code point U+0100 corresponds to decimal 256. Modern Unicode now encompasses far more code points beyond this arrangement.

In cryptography, the term AES-256 denotes a widely used encryption standard with a 256-bit key length, illustrating how the number 256 appears in contemporary security technologies. Overall, 256 is a key boundary and unit in computing, mathematics, and data representation.

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