Recognised as Number
805
- Positive
- Odd
- Composite
- 3 digits
805 is an odd 3-digit integer and a composite number. It has 8 divisors and a digital root of 4.
Number properties
ParityOddnot divisible by 2
SignPositive
PrimalityComposite
Absolute value805
Digit count3
Digit sum13
Digit product0zero, because one of the digits is zero
Multiplicative persistence1times the digit product can be taken before one digit is left
Digital root4repeated digit sum
PalindromicNoreads differently backwards
Happy numberNosquared-digit sums reach 1
Harshad numberNodivisible by its own digit sum
Factors & divisors
Prime factorisation5 × 7 × 23
Distinct prime factors35, 7, 23
Number of divisors8
Sum of divisors σ(n)1,152
Aliquot sum347sum of the proper divisors
ClassificationDeficientthe aliquot sum is less than the number
Euler's totient φ(n)528integers below n that share no factor with it
Carmichael function λ(n)132the smallest exponent with aˣ ≡ 1 for every unit; smaller than φ(n) = 528
Möbius function μ(n)−13 distinct prime factors, an odd number of them
SquarefreeYesno repeated prime factor
All divisors1, 5, 7, 23, 35, 115, 161, 8058 in total
Arithmetic
Representations
Decimal805
Binary110010010110 bits
Octal1445
Hexadecimal325
Base 36MD
Roman numeralDCCCV
In wordseight hundred and five
Ordinaleight hundred and fifth
Scientific notation8.05 × 10^2
Engineering notation805
In other bases
Ternary1002211base 3; the most digit-efficient integer base after e: 7 digits
Quinary11210base 5; one hand: 5 digits
Septenary2230base 7: 4 digits
Nonary1084base 9; each digit is two ternary digits: 4 digits
Duodecimal571base 12; divides by 2, 3, 4 and 6, which is why eggs and inches come in twelves: 3 digits
Vigesimal205base 20; hands and feet, and the Mayan and Yoruba systems: 3 digits
Sexagesimal13:25base 60; Babylonian, and still how an hour and a circle are divided: 2 digits
Balanced ternary1010T11digits −1, 0 and +1 written T, 0 and 1; negation is swapping T and 1, so no sign is needed
Negabinary11101100101base −2; place values alternate 1, −2, 4, −8, so every integer has exactly one form without a sign
Bit-level
0000001100100101
Bit length10 bitsto write the magnitude
Set bits5the population count, or Hamming weight
Zero bits5within that length
Bit parityodd5 set bits, so odd; not the same as the number itself being odd
Highest set bitbit 9worth 512
Lowest set bitbit 00 trailing zeros
Power of twoNo
Bytes203 25
Gray code1010110111n XOR (n >> 1); successive values differ in exactly one bit
At each machine width
16-bit0000001100100101
32-bit00000000000000000000001100100101
64-bit0000000000000000000000000000000000000000000000000000001100100101
One's complement1111110011011010at 16 bits, every bit flipped
Bits reversed1010010011000000at 16 bits
Rotated left by 10000011001001010at 16 bits, wrapping
Shifted left by 111001001010= 1,610, no wrap
Shifted right by 1110010010= 402, discarding the low bit
These bits as a double3.97722845 × 10^-321≈IEEE-754 binary64 reinterpretation of the same 64 bits (subnormal)
Nearest landmarks
Powers & multiples
805 to the power 2648,025
805 to the power 3521,660,125
805 to the power 4419,936,400,625
805 to the power 5338,048,802,503,125
First ten multiples805, 1,610, 2,415, 3,220, 4,025, 4,830, 5,635, 6,440, 7,245, 8,050
Powers of twoBetween 2^9 (512) and 2^10 (1,024)
Divisibility tests
Divisible by 2No, remainder 1
Divisible by 3No, remainder 1
Divisible by 4No, remainder 1
Divisible by 5Yes
Divisible by 6No, remainder 1
Divisible by 7Yes
Divisible by 8No, remainder 5
Divisible by 9No, remainder 4
Divisible by 10No, remainder 5
Divisible by 11No, remainder 2
Divisible by 12No, remainder 1
Divisible by 100No, remainder 5
Collatz (3n + 1) trajectory
Steps to reach 120the total stopping time
Reaches 1Yesthe Collatz conjecture says every positive integer does, but it is unproven
First steps805 → 2,416 → 1,208 → 604 → 302 → 151 → 454 → 227 → 682 → 341 → …
Last steps… → 32 → 16 → 8 → 4 → 2 → 1
As a percentage & fraction
As a percentage80,500%
805% as a decimal8.05
805% of 100805
805% of 1,0008,050
As a fraction of 100805/100
Read another way
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Derived from 805
Other readings
Also reads as
#880055 (colour)
- #880055
- Magenta
- Dark
- Nearest: Medium violet red
#880055 is a magenta with RGB values 136, 0, 85 and HSL 323°, 100%, 27%. It is a dark colour, so white text on it reaches 9.6:1 contrast (AAA for normal text). The nearest named colour is Medium violet red.
Colour values
#880055#880055
HEX#880055
HEX (short)#805
RGBrgb(136, 0, 85)
RGB (0–1)0.5333, 0, 0.3333
RGB percentages53.3%, 0%, 33.3%
HSLhsl(322.5, 100%, 26.7%)
HSV / HSBhsv(322.5, 100%, 53.3%)
CMYK0%, 100%, 37.5%, 46.7%≈naive device-independent conversion; real print needs an ICC profile
24-bit integer8,912,981
CSS custom property--colour: #880055;
Brightness & contrast
Relative luminance0.0589WCAG 2.x, 0 is black and 1 is white
Perceived brightness79.7 of 255ITU-R BT.601 weighting
Light or darkDark
Best text colour on this backgroundWhitecontrast 9.64:1
Contrast with white9.64:1WCAG normal text: AAA
Contrast with black2.18:1WCAG normal text: Fail
Greyscale equivalent#232323
Inverted#77FFAA
Colour vision & accessibility
Distinguishable without hueShifts in lightness toonever rely on hue alone to carry meaning
Contrast with white, large text9.64:1WCAG large text: AAA
Contrast with black, large text2.18:1WCAG large text: Fail
Named colours
Hue familymagenta
CSS keyword usableNo exact keyword
Colour harmonies
Complementary#008833
Analogous#770088, #880011
Triadic#558800, #005588
Split complementary#118800, #008877
Tetradic#887700, #008833, #001188
Tints, shades & saturation
Channel breakdown
R136
G0
B85
Red136 (53.3%)
Green0 (0%)
Blue85 (33.3%)
Hue322.5°
Saturation (HSL)100%
Lightness26.67%
Dominant channelRed
Hex per channelR 88 · G 00 · B 55
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Harmonies
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