Number

128

128 is a composite number, even, a calendar year.

128 (one hundred twenty-eight) is an even 3-digit number. It is a composite number with 8 divisors, and factors as 2⁷. It is a power of two (2⁷). Written other ways, in Roman numerals it is CXXVIII and in binary, 10000000.

Ascending Digits Deficient Number Frugal Number Odious Number Power of Two Powerful Number Practical Number Recamán's Sequence Refactorable Number Year Zuckerman Number

Interestingness

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8 notable facts · grade A

116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140

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Historical context — 128 AD

Calendar year

Year 128 (CXXVIII) was a leap year starting on Wednesday of the Julian calendar.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 Read the full article on Wikipedia →

Historical context — 128 BC

Calendar year

Year 128 BC was a year of the pre-Julian Roman calendar.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 Read the full article on Wikipedia →

Year facts

Year type: Leap year
Divisible by 4 and not by 100; February has 29 days.
Days in year: 366
ISO weeks: 53
Long year: contains 53 ISO weeks.
Started on: Thursday
January 1, 128
Ended on: Friday
December 31, 128
Friday the 13ths: 2
2 Friday the 13ths this year.
Decade: 120s
120–129
Century: 2nd century
101–200
Millennium: 1st millennium
1–1000
Years ago: 1,898
1898 years before 2026.

In other calendars

Hebrew: 3888 / 3889 AM
Rosh Hashanah falls in September/October.
Chinese: Year of the zodiac:Earth zodiac:Dragon
Sexagenary cycle position 5 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 671 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Ethiopian: 120 / 121 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 50 / 49 Saka
Indian national calendar; year starts in March.

Properties

Parity: Even
Digit count: 3
Digit sum: 11
Digit product: 16
Digital root: 2
Palindrome: No
Bit width: 8 bits
Reversed: 821
Recamán's sequence: a(144) = 128
Square (n²): 16,384
Cube (n³): 2,097,152
Divisor count: 8
σ(n) — sum of divisors: 255
φ(n) — Euler's totient: 64
Sum of prime factors: 14

Primality

Prime factorization: 2 ⁷

Nearest primes: 127 (−1) · 131 (+3)

Divisors & multiples

All divisors (8)

1 · 2 · 4 · 8 · 16 · 32 · 64 (half) · 128

Aliquot sum (sum of proper divisors): 127

Factor pairs (a × b = 128)

1 × 128

2 × 64

4 × 32

8 × 16

First multiples

128 · 256 (double) · 384 · 512 · 640 · 768 · 896 · 1,024 · 1,152 · 1,280

Sums & aliquot sequence

As a sum of two squares: 8² + 8²

As a sum of two cubes: 4³ + 4³

Aliquot sequence: 128 → 127 → 1 → 0 — terminates at zero

Continued fraction of √n

√128 = [11; (3, 5, 3, 22)]

Period length 4 — the block in parentheses repeats forever.

Representations

In words: one hundred twenty-eight
Ordinal: 128th
Roman numeral: CXXVIII
Binary: 10000000
Octal: 200
Hexadecimal: 0x80
Base64: gA==
One's complement: 127 (8-bit)
Scientific notation: 1.28 × 10²
As a duration: 128 s = 2 minutes, 8 seconds

In other bases

ternary (3) 11202

quaternary (4) 2000

quinary (5) 1003

senary (6) 332

septenary (7) 242

nonary (9) 152

undecimal (11) 107

duodecimal (12) a8

tridecimal (13) 9b

tetradecimal (14) 92

pentadecimal (15) 88

Palindromic in base 7

As an angle

128°

128° ≈ 2.234 rad

Compass bearing: SE (southeast)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒁹𒁹 𒁹𒁹𒁹𒁹𒁹𒁹𒁹𒁹
Egyptian hieroglyphic: 𓍢𓎆𓎆𓏺𓏺𓏺𓏺𓏺𓏺𓏺𓏺
Greek (Milesian): ρκηʹ
Mayan (base 20): 𝋦·𝋨
Chinese: 一百二十八
Chinese (financial): 壹佰貳拾捌

In other modern scripts

Eastern Arabic ١٢٨ Devanagari १२८ Bengali ১২৮ Tamil ௧௨௮ Thai ๑๒๘ Tibetan ༡༢༨ Khmer ១២៨ Lao ໑໒໘ Burmese ၁၂၈

Digit at this position in famous constants

π — Pi (π): Digit 128 = 6
e — Euler's number (e): Digit 128 = 5
φ — Golden ratio (φ): Digit 128 = 8
√2 — Pythagoras's (√2): Digit 128 = 0
ln 2 — Natural log of 2: Digit 128 = 2
γ — Euler-Mascheroni (γ): Digit 128 = 0

Also seen as

Goldbach decomposition

Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 128, here are decompositions:

19 + 109 = 128
31 + 97 = 128
61 + 67 = 128

Unicode codepoint

U+0080

Control character (Cc)

UTF-8 encoding: C2 80 (2 bytes).

Lookup U+0080 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#000080

RGB(0, 0, 128)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.0.128.

Address: 0.0.0.128
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.0.128

Unspecified address (0.0.0.0/8) — "this network" placeholder.

Musical pitch

Heard as a frequency, 128 Hz is closest to:

Concert pitch (A4 = 440 Hz): C3 (130.8 Hz, -38¢)
Scientific pitch (C4 = 256 Hz): C3 (128 Hz, exact)
Baroque pitch (A4 = 415 Hz): C♯3 (130.7 Hz, -36¢)