# 127 number

127 is the natural number following 126 and preceding 128.

 Template:Numbers 120s Cardinal One hundred [and] twenty-seven Ordinal 127th Factorization prime number Roman numeral CXXVII Binary 1111111 Hexadecimal 7F

## In mathematics

One hundred [and] twenty-seven 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 ${\displaystyle p=(x^{3}-y^{3})/(x-y)}$, ${\displaystyle x=y+1}$. 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 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.

## 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" (Holy Bible, Esther 1:1).
• The number of sons of Bethlehem at the Census of men of Israel upon return from exile (Holy Bible, Ezra 2:21).
• The year AD 127 or 127 BC.