Number
813
- Positive
- Odd
- Composite
- 3 digits
813 is an odd 3-digit integer and a composite number. It has 4 divisors and a digital root of 3.
Number properties
ParityOddnot divisible by 2
SignPositive
PrimalityComposite
Absolute value813
Digit count3
Digit sum12
Digital root3repeated digit sum
PalindromicNoreads differently backwards
Happy numberNosquared-digit sums reach 1
Harshad numberNodivisible by its own digit sum
Factors & divisors
Prime factorisation3 × 271
Distinct prime factors23, 271
Number of divisors4
Sum of divisors σ(n)1,088
Aliquot sum275sum of the proper divisors
ClassificationDeficientthe aliquot sum is less than the number
Euler's totient φ(n)540integers below n that share no factor with it
SquarefreeYesno repeated prime factor
All divisors1, 3, 271, 8134 in total
Arithmetic
Representations
Decimal813
Binary110010110110 bits
Octal1455
Hexadecimal32D
Base 36ML
Roman numeralDCCCXIII
In wordseight hundred and thirteen
Ordinaleight hundred and thirteenth
Scientific notation8.13 × 10^2
Engineering notation813
Nearest landmarks
Powers & multiples
813 to the power 2660,969
813 to the power 3537,367,797
813 to the power 4436,880,018,961
813 to the power 5355,183,455,415,293
First ten multiples813, 1,626, 2,439, 3,252, 4,065, 4,878, 5,691, 6,504, 7,317, 8,130
Powers of twoBetween 2^9 (512) and 2^10 (1,024)
Divisibility tests
Divisible by 2No, remainder 1
Divisible by 3Yes
Divisible by 4No, remainder 1
Divisible by 5No, remainder 3
Divisible by 6No, remainder 3
Divisible by 7No, remainder 1
Divisible by 8No, remainder 5
Divisible by 9No, remainder 3
Divisible by 10No, remainder 3
Divisible by 11No, remainder 10
Divisible by 12No, remainder 9
Divisible by 100No, remainder 13
Collatz (3n + 1) trajectory
Steps to reach 141the total stopping time
Reaches 1Yesthe Collatz conjecture says every positive integer does, but it is unproven
First steps813 → 2,440 → 1,220 → 610 → 305 → 916 → 458 → 229 → 688 → 344 → …
Last steps… → 5 → 16 → 8 → 4 → 2 → 1
As a percentage & fraction
As a percentage81,300%
813% as a decimal8.13
813% of 100813
813% of 1,0008,130
As a fraction of 100813/100
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Derived from 813
Other readings
Also reads as
#881133 (colour)
- #881133
- Red
- Dark
- Nearest: Brown
#881133 is a red with RGB values 136, 17, 51 and HSL 343°, 78%, 30%. It is a dark colour, so white text on it reaches 9.7:1 contrast (AAA for normal text). The nearest named colour is Brown.
Colour values
#881133#881133
HEX#881133
HEX (short)#813
RGBrgb(136, 17, 51)
RGB (0–1)0.5333, 0.0667, 0.2
RGB percentages53.3%, 6.7%, 20%
HSLhsl(342.9, 77.8%, 30%)
HSV / HSBhsv(342.9, 87.5%, 53.3%)
CMYK0%, 87.5%, 62.5%, 46.7%≈naive device-independent conversion; real print needs an ICC profile
24-bit integer8,917,299
CSS custom property--colour: #881133;
Brightness & contrast
Relative luminance0.05874WCAG 2.x, 0 is black and 1 is white
Perceived brightness77.4 of 255ITU-R BT.601 weighting
Light or darkDark
Best text colour on this backgroundWhitecontrast 9.66:1
Contrast with white9.66:1WCAG normal text: AAA
Contrast with black2.17:1WCAG normal text: Fail
Greyscale equivalent#2D2D2D
Inverted#77EECC
Colour vision & accessibility
Distinguishable without hueShifts in lightness toonever rely on hue alone to carry meaning
Contrast with white, large text9.66:1WCAG large text: AAA
Contrast with black, large text2.17:1WCAG large text: Fail
Named colours
Hue familyred
CSS keyword usableNo exact keyword
Colour harmonies
Complementary#118866
Analogous#88116E, #882A11
Triadic#338811, #113388
Split complementary#11882A, #116E88
Tetradic#6F8811, #118866, #2B1188
Tints, shades & saturation
Channel breakdown
R136
G17
B51
Red136 (53.3%)
Green17 (6.7%)
Blue51 (20%)
Hue342.86°
Saturation (HSL)77.78%
Lightness30%
Dominant channelRed
Hex per channelR 88 · G 11 · B 33
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