127

127, written as one hundred twenty-seven, is a natural number that follows 126 and precedes 128. It is odd and is a prime number—the 31st prime in the sequence of primes.

Mathematically, 127 is a Mersenne prime, since it can be written as 2^7 − 1. Its binary form is 1111111. It is also prime in various bases, for example 11201 in base 3 and CXXVII in Roman numerals.

In computing, 127 is notable as the maximum value of a signed 8-bit integer. It is also the largest value encoded by a 7-bit ASCII character set, where 127 corresponds to the DEL control code. In hexadecimal, this value is 0x7F.

127 appears in culture and science as well. Messier 127 (M127) is a galaxy in the constellation Coma Berenices. The number is also associated with the film 127 Hours, which recounts a climber's ordeal lasting that many hours.

Calendar usage: in the Gregorian calendar, the 127th day of a common year falls on May 7, while in leap years it falls on May 6. The number is used in various technical specifications to denote a maximum seven-bit value in data formats and MIDI.