Number
221
- Positive
- Odd
- Composite
- 3 digits
221 is an odd 3-digit integer and a composite number. It has 4 divisors and a digital root of 5.
Number properties
ParityOddnot divisible by 2
SignPositive
PrimalityComposite
Absolute value221
Digit count3
Digit sum5
Digital root5repeated digit sum
PalindromicNoreads differently backwards
Happy numberNosquared-digit sums reach 1
Harshad numberNodivisible by its own digit sum
Factors & divisors
Prime factorisation13 × 17
Distinct prime factors213, 17
Number of divisors4
Sum of divisors σ(n)252
Aliquot sum31sum of the proper divisors
ClassificationDeficientthe aliquot sum is less than the number
Euler's totient φ(n)192integers below n that share no factor with it
SquarefreeYesno repeated prime factor
All divisors1, 13, 17, 2214 in total
Arithmetic
Representations
Decimal221
Binary110111018 bits
Octal335
HexadecimalDD
Base 3665
Roman numeralCCXXI
In wordstwo hundred and twenty-one
Ordinaltwo hundred and twenty-first
Scientific notation2.21 × 10^2
Engineering notation221
Nearest landmarks
Powers & multiples
221 to the power 248,841
221 to the power 310,793,861
221 to the power 42,385,443,281
221 to the power 5527,182,965,101
First ten multiples221, 442, 663, 884, 1,105, 1,326, 1,547, 1,768, 1,989, 2,210
Powers of twoBetween 2^7 (128) and 2^8 (256)
Divisibility tests
Divisible by 2No, remainder 1
Divisible by 3No, remainder 2
Divisible by 4No, remainder 1
Divisible by 5No, remainder 1
Divisible by 6No, remainder 5
Divisible by 7No, remainder 4
Divisible by 8No, remainder 5
Divisible by 9No, remainder 5
Divisible by 10No, remainder 1
Divisible by 11No, remainder 1
Divisible by 12No, remainder 5
Divisible by 100No, remainder 21
Collatz (3n + 1) trajectory
Steps to reach 1114the total stopping time
Reaches 1Yesthe Collatz conjecture says every positive integer does, but it is unproven
First steps221 → 664 → 332 → 166 → 83 → 250 → 125 → 376 → 188 → 94 → …
Last steps… → 5 → 16 → 8 → 4 → 2 → 1
As a percentage & fraction
As a percentage22,100%
221% as a decimal2.21
221% of 100221
221% of 1,0002,210
As a fraction of 100221/100
Read another way
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Derived from 221
Other readings
Also reads as
#222211 (colour)
- #222211
- Yellow
- Dark
- Nearest: Black
#222211 is a yellow with RGB values 34, 34, 17 and HSL 60°, 33%, 10%. It is a dark colour, so white text on it reaches 16.1:1 contrast (AAA for normal text). The nearest named colour is Black.
Colour values
#222211#222211
HEX#222211
HEX (short)#221
RGBrgb(34, 34, 17)
RGB (0–1)0.1333, 0.1333, 0.0667
RGB percentages13.3%, 13.3%, 6.7%
HSLhsl(60, 33.3%, 10%)
HSV / HSBhsv(60, 50%, 13.3%)
CMYK0%, 0%, 50%, 86.7%≈naive device-independent conversion; real print needs an ICC profile
24-bit integer2,236,945
CSS custom property--colour: #222211;
Brightness & contrast
Relative luminance0.01525WCAG 2.x, 0 is black and 1 is white
Perceived brightness32.5 of 255ITU-R BT.601 weighting
Light or darkDark
Best text colour on this backgroundWhitecontrast 16.09:1
Contrast with white16.09:1WCAG normal text: AAA
Contrast with black1.3:1WCAG normal text: Fail
Greyscale equivalent#212121
Inverted#DDDDEE
Colour vision & accessibility
Distinguishable without hueYesnever rely on hue alone to carry meaning
Contrast with white, large text16.09:1WCAG large text: AAA
Contrast with black, large text1.3:1WCAG large text: Fail
Named colours
Hue familyyellow
CSS keyword usableNo exact keyword
Colour harmonies
Complementary#111122
Analogous#221A11, #1A2211
Triadic#112222, #221122
Split complementary#111A22, #1A1122
Tetradic#11221A, #111122, #22111A
Tints, shades & saturation
Channel breakdown
R34
G34
B17
Red34 (13.3%)
Green34 (13.3%)
Blue17 (6.7%)
Hue60°
Saturation (HSL)33.33%
Lightness10%
Dominant channelRed and Green
Hex per channelR 22 · G 22 · B 11
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Harmonies
Similar named colours
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