9223372036854775807

9223372036854775807, commonly written as 9,223,372,036,854,775,807, is the maximum value of a signed 64-bit integer in two's complement representation. It equals 2^63 - 1 and serves as the positive bound for 64-bit signed integers in many programming environments.

In two's complement systems, the 64-bit signed integer range runs from -2^63 to 2^63 - 1, i.e., from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807. The lowest negative value, -2^63, has no positive counterpart in this representation. This arrangement means that adding one to the maximum value yields an overflow in typical arithmetic contexts.

This value is widely used as the upper bound for positive values in programming languages and libraries that implement 64-bit signed integers. Examples include Java's long type, whose maximum is 9223372036854775807, and the C/C++ 64-bit integer type int64_t, defined as INT64_MAX with the same magnitude. It often appears as a constant, a sentinel, or a boundary in algorithms, data structures, and serialization formats.

For comparison, the corresponding unsigned 64-bit maximum is 18446744073709551615, the full range of 64-bit unsigned integers, which differs because the sign bit is not used for magnitude in unsigned types.

See also: powers of two, 2^63 - 1, 2^64 - 1, int64, long long, Long.MAX_VALUE, INT64_MAX.