127 is the natural number following 126 and preceding 128.

Cardinal	One hundred * twenty-seven
Ordinal	127th
Factorization	prime
Roman numeral	CXXVII
Binary	1111111
Hexadecimal	7F

In mathematics

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127 is a Mersenne prime, 2⁷ - 1, and as such, in binary it is a repunit prime, a permutable prime and a palindromic prime. This also means it is the largest integer that can be represented by a signed byte. As a Mersenne prime, 127 is related to the perfect number 8128, and 2¹²⁷ - 1 is also a Mersenne prime, making it a double Mersenne prime. 127 is also a cuban prime of the form $p\; =\; (x^3\; -\; y^3)\; /\; (x\; -\; y)$, $x\; =\; y\; +\; 1$. The next prime is 131, with which it comprises a cousin prime. Because the next odd number, 129, is a semiprime, 127 is a Chen prime. 127 is greater than the arithmetic mean of its two neighboring primes, thus it's a strong prime.

It is the sum of the sums of divisors of the first twelve integers.

127 is a centered hexagonal number.

It is the 7th Motzkin number.

It is a nice Friedman number in base 10, since 127 = -1 + 2⁷, as well as binary since 1111111 = (1 + 1)¹¹¹ - 1 * 1.

It should also be noted that 2¹²⁷ - 1 is also a Mersenne prime, discovered by Lucas in 1876. 2¹²⁷ - 1 held the record for the largest known prime for 75 years, and it is the largest prime ever discovered by hand calculations. 2¹²⁷ - 1 is a double Mersenne prime.

In other fields

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One hundred ^* twenty-seven is also:

• ASCII and Unicode code point for delete.
• The number of provinces ruled by King Xerxes I, "from India to Ethiopia" (Bible, Esther 1:1).
• The number of sons of Bethlehem at the Census of men of Israel upon return from exile (Bible, Ezra 2:21).
• The year AD 127 or 127 BC.

Integers

Ciento veintisiete | 127 (nombre) | 127 | 127 | 127 (число) | 127 (število) | 127 (tal) | 127