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Number

668

  • Positive
  • Even
  • Composite
  • 3 digits

668 is an even 3-digit integer and a composite number. It has 6 divisors and a digital root of 2.

Number properties

ParityEvendivisible by 2
SignPositive
PrimalityComposite
Absolute value668
Digit count3
Digit sum20
Digital root2repeated digit sum
PalindromicNoreads differently backwards
Happy numberNosquared-digit sums reach 1
Harshad numberNodivisible by its own digit sum

Factors & divisors

Prime factorisation2^2 × 167
Distinct prime factors22, 167
Number of divisors6
Sum of divisors σ(n)1,176
Aliquot sum508sum of the proper divisors
ClassificationDeficientthe aliquot sum is less than the number
Euler's totient φ(n)332integers below n that share no factor with it
SquarefreeNohas a repeated prime factor
All divisors1, 2, 4, 167, 334, 6686 in total

Arithmetic

Previous number667
Next number669
Double1,336
Half334
Square446,224
Cube298,077,632
Square root25.845695967≈irrational, shown to 9 decimal places
Cube root8.741624639≈
Negation-668
Reciprocal0.001497006≈
668 factorial4502931767177512390692414025435152323393… (1,599 digits)

Representations

Decimal668
Binary101001110010 bits
Octal1234
Hexadecimal29C
Base 36IK
Roman numeralDCLXVIII
In wordssix hundred and sixty-eight
Ordinalsix hundred and sixty-eighth
Scientific notation6.68 × 10^2
Engineering notation668

Nearest landmarks

Next prime673+5
Previous prime661−7
Distance to nearest prime5
Nearest square below625
Nearest square above676

Powers & multiples

668 to the power 2446,224
668 to the power 3298,077,632
668 to the power 4199,115,858,176
668 to the power 5133,009,393,261,568
First ten multiples668, 1,336, 2,004, 2,672, 3,340, 4,008, 4,676, 5,344, 6,012, 6,680
Powers of twoBetween 2^9 (512) and 2^10 (1,024)

Divisibility tests

Divisible by 2Yes
Divisible by 3No, remainder 2
Divisible by 4Yes
Divisible by 5No, remainder 3
Divisible by 6No, remainder 2
Divisible by 7No, remainder 3
Divisible by 8No, remainder 4
Divisible by 9No, remainder 2
Divisible by 10No, remainder 8
Divisible by 11No, remainder 8
Divisible by 12No, remainder 8
Divisible by 100No, remainder 68

Collatz (3n + 1) trajectory

Steps to reach 169the total stopping time
Highest value reached9,23213× the starting value
Reaches 1Yesthe Collatz conjecture says every positive integer does, but it is unproven
First steps668 → 334 → 167 → 502 → 251 → 754 → 377 → 1,132 → 566 → 283 → …
Last steps… → 5 → 16 → 8 → 4 → 2 → 1

As a percentage & fraction

As a percentage66,800%
668% as a decimal6.68
668% of 100668
668% of 1,0006,680
As a fraction of 100668/100

Read another way

As seconds11 minutes and 8 seconds
As bytes668 B
As a 24-bit colour#00029C

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Neighbouring numbers

Nearby primes

Also reads as

#666688 (colour)

  • #666688
  • Blue
  • Dark
  • Nearest: Slate grey

#666688 is a blue with RGB values 102, 102, 136 and HSL 240°, 14%, 47%. It is a dark colour, so white text on it reaches 5.5:1 contrast (AA for normal text). The nearest named colour is Slate grey.

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Colour values

#666688#666688
HEX#666688
HEX (short)#668
RGBrgb(102, 102, 136)
RGB (0–1)0.4, 0.4, 0.5333
RGB percentages40%, 40%, 53.3%
HSLhsl(240, 14.3%, 46.7%)
HSV / HSBhsv(240, 25%, 53.3%)
CMYK25%, 25%, 0%, 46.7%≈naive device-independent conversion; real print needs an ICC profile
24-bit integer6,710,920
CSS custom property--colour: #666688;

Brightness & contrast

Relative luminance0.14105WCAG 2.x, 0 is black and 1 is white
Perceived brightness106.4 of 255ITU-R BT.601 weighting
Light or darkDark
Best text colour on this backgroundWhitecontrast 5.5:1
Contrast with white5.5:1WCAG normal text: AA
Contrast with black3.82:1WCAG normal text: Fail
Greyscale equivalent#686868
Inverted#999977

Colour vision & accessibility

Normal visionProtanopiaDeuteranopiaTritanopia
Protanopia#5D6A89no red cones; affects about 1% of men; ΔE 5.1 from the original
Deuteranopia#5C6887no green cones; the most common form, about 1% of men; ΔE 4.7 from the original
Tritanopia#5E6C72no blue cones; rare, and affects men and women equally; ΔE 18 from the original
Distinguishable without hueYesnever rely on hue alone to carry meaning
Contrast with white, large text5.5:1WCAG large text: AAA
Contrast with black, large text3.82:1WCAG large text: AA

Named colours

Slate grey · ΔE 15.5Light slate grey · ΔE 17.2Steel blue · ΔE 19.8Dim grey · ΔE 20.4Gray · ΔE 22.3Dark slate grey · ΔE 28
Nearest named CSS colourSlate grey (#708090)ΔE 15.5, a distinctly different colour
Hue familyblue
CSS keyword usableNo exact keyword

Colour harmonies

base+30°+90°+120°+180°+210°+240°+270°+330°
Complementary#888866
Analogous#667788, #776688
Triadic#886666, #668866
Split complementary#887766, #778866
Tetradic#886677, #888866, #668877

Tints, shades & saturation

+40%+30%+20%+10%base-10%-20%-30%-40%
Lighter +40%#D8D8E2
Lighter +30%#BBBBCC
Lighter +20%#9E9EB6
Lighter +10%#8181A0
Darker −10%#50506B
Darker −20%#3A3A4E
Darker −30%#242431
Darker −40%#0F0F13
More saturated +25%#4848A6
Less saturated −25%#777777

Channel breakdown

R102
G102
B136
Red102 (40%)
Green102 (40%)
Blue136 (53.3%)
Hue240°
Saturation (HSL)14.29%
Lightness46.67%
Dominant channelBlue
Hex per channelR 66 · G 66 · B 88

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Every value on this page was computed from “668” by Nerdulator’s number engine. Nothing here was retrieved from a database of answers or written by a model.