128 (NUMBER)

'128' is the natural number following 127 and preceding 129.

Cardinal	One hundred [and] twenty-eight
Ordinal	128th
Factorization	$2^7$
Divisors	1 2 4 8 16 32 64
Roman numeral	CXXVIII
Binary	10000000
Hexadecimal	80

Contents

In mathematics

In other fields

References

In mathematics

'One hundred [and] twenty-eight' is the seventh power of 2. It is the largest number which can not be expressed as the sum of any number of distinct squares. But it is divisible by the total number of its divisors, making it a refactorable number.
The sum of Euler's totient function φ(''x'') over the first twenty integers is 128.
128 can be expressed by a combination of its digits with mathematical operators thus 128 = 2^{8 - 1}, making it a Friedman number in base 10. 128 is a Zuckerman number in bases 7, 10 and 15.

In other fields

'One hundred [and] twenty-eight' is also:

★ The size, in bits, of certain integer data types, used in computer representations of numbers.

★ The number of character codes in ASCII (a 7-bit, not 8-bit, code).

★ Any bit with a binary prefix is 128 bytes of a lesser binary prefix value. For example, 1 gibibit is 128 mebibytes.

★ In mebibytes, a common size for USB flash drives and memory cards.

★ IPv6 uses 128-bit (16-byte) addresses.

★ The number of sons of Anathoth at the Census of men of Israel upon return from exile (the Bible, Ezra 2:23). Also, the number of singers, sons of Asaph (Ezra 2:41).

★ The number of musical instruments specified in General MIDI. Sometimes they are numbered 0 to 127 and sometimes they are numbered 1 to 128.

★ The year 128 AD or 128 BC.

References

★ Wells, D. ''The Penguin Dictionary of Curious and Interesting Numbers'' London: Penguin Group. (1987): 138