127 (number)

From Wikipedia, the free encyclopedia

127 is the natural number following 126 and preceding 128.

<< 120 121 122 123 124 125 126 127 128 129 >> List of numbers — Integers << 100 110 120 130 140 150 160 170 180 190 >>
Cardinal	One hundred [and] twenty-seven
Ordinal	127th
Factorization	prime
Roman numeral	CXXVII
Binary	1111111
Hexadecimal	7F

[edit] In mathematics

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. 127 is also an exponent for the Mersenne prime 2¹²⁷ - 1, making 127 a double Mersenne prime. (2¹²⁷ - 1 was discovered by Edouard Lucas in 1876, and held the record for the largest known prime for 75 years. It's still the largest prime ever discovered by hand calculations.)

127 is also a cuban prime of the form p = (x³ − y³) / (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.

[edit] In other fields

One hundred [and] 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.