Number

640

Positive
Even
Composite
3 digits

640 is an even 3-digit integer and a composite number. It has 16 divisors and a digital root of 1.

The canonical address for this page is /640.

Number properties

ParityEvendivisible by 2

SignPositive

PrimalityComposite

Absolute value640

Digit count3

Digit sum10

Digital root1repeated digit sum

PalindromicNoreads differently backwards

Happy numberNosquared-digit sums reach 1

Harshad numberYesdivisible by its own digit sum

Factors & divisors

Prime factorisation2^7 × 5

Distinct prime factors22, 5

Number of divisors16

Sum of divisors σ(n)1,530

Aliquot sum890sum of the proper divisors

ClassificationAbundantthe aliquot sum exceeds the number

Euler's totient φ(n)256integers below n that share no factor with it

SquarefreeNohas a repeated prime factor

All divisors1, 2, 4, 5, 8, 10, 16, 20, 32, 40, 64, 80, 128, 160, 320, 64016 in total

Arithmetic

Previous number639

Next number641

Double1,280

Half320

Square409,600

Cube262,144,000

Square root25.298221281≈irrational, shown to 9 decimal places

Cube root8.61773876≈

Negation-640

Reciprocal0.0015625≈

640 factorial6440971856520001805513180096598153272178… (1,520 digits)

Representations

Decimal640

Binary101000000010 bits

Octal1200

Hexadecimal280

Base 36HS

Roman numeralDCXL

In wordssix hundred and forty

Ordinalsix hundred and fortieth

Scientific notation6.4 × 10^2

Engineering notation640

Nearest landmarks

Next prime641+1

Previous prime631−9

Distance to nearest prime1

Nearest square below625

Nearest square above676

Powers & multiples

640 to the power 2409,600

640 to the power 3262,144,000

640 to the power 4167,772,160,000

640 to the power 5107,374,182,400,000

First ten multiples640, 1,280, 1,920, 2,560, 3,200, 3,840, 4,480, 5,120, 5,760, 6,400

Powers of twoBetween 2^9 (512) and 2^10 (1,024)

Divisibility tests

Divisible by 2Yes

Divisible by 3No, remainder 1

Divisible by 4Yes

Divisible by 5Yes

Divisible by 6No, remainder 4

Divisible by 7No, remainder 3

Divisible by 8Yes

Divisible by 9No, remainder 1

Divisible by 10Yes

Divisible by 11No, remainder 2

Divisible by 12No, remainder 4

Divisible by 100No, remainder 40

Collatz (3n + 1) trajectory

Steps to reach 112the total stopping time

Highest value reached640

Reaches 1Yesthe Collatz conjecture says every positive integer does, but it is unproven

First steps640 → 320 → 160 → 80 → 40 → 20 → 10 → 5 → 16 → 8 → …

Last steps… → 5 → 16 → 8 → 4 → 2 → 1

As a percentage & fraction

As a percentage64,000%

640% as a decimal6.4

640% of 100640

640% of 1,0006,400

As a fraction of 100640/100

Read another way

As seconds10 minutes and 40 seconds

As bytes640 B

As a 24-bit colour#000280

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Neighbouring numbers

Derived from 640

Nearby primes

#000640 (colour)

#000640
Blue
Dark
Nearest: Midnight blue

#000640 is a blue with RGB values 0, 6, 64 and HSL 234°, 100%, 13%. It is a dark colour, so white text on it reaches 19.1:1 contrast (AAA for normal text). The nearest named colour is Midnight blue.

Open this reading on its own page →

Colour values

#000640#000640

HEX#000640

RGBrgb(0, 6, 64)

RGB (0–1)0, 0.0235, 0.251

RGB percentages0%, 2.4%, 25.1%

HSLhsl(234.4, 100%, 12.5%)

HSV / HSBhsv(234.4, 100%, 25.1%)

CMYK100%, 90.6%, 0%, 74.9%≈naive device-independent conversion; real print needs an ICC profile

24-bit integer1,600

CSS custom property--colour: #000640;

Brightness & contrast

Relative luminance0.005WCAG 2.x, 0 is black and 1 is white

Perceived brightness22.1 of 255ITU-R BT.601 weighting

Light or darkDark

Best text colour on this backgroundWhitecontrast 19.09:1

Contrast with white19.09:1WCAG normal text: AAA

Contrast with black1.1:1WCAG normal text: Fail

Greyscale equivalent#090909

Inverted#FFF9BF

Colour vision & accessibility

Normal vision Protanopia Deuteranopia Tritanopia

Protanopia#001342no red cones; affects about 1% of men; ΔE 8 from the original

Deuteranopia#000C3Fno green cones; the most common form, about 1% of men; ΔE 4.3 from the original

Tritanopia#001823no blue cones; rare, and affects men and women equally; ΔE 35.8 from the original

Distinguishable without hueYesnever rely on hue alone to carry meaning

Contrast with white, large text19.09:1WCAG large text: AAA

Contrast with black, large text1.1:1WCAG large text: Fail

Named colours

Midnight blue · ΔE 21 Dark slateblue · ΔE 27.6 Rebecca purple · ΔE 37.8 Indigo · ΔE 39 Navy · ΔE 40.3 Black · ΔE 41.6

Nearest named CSS colourMidnight blue (#191970)ΔE 20.98, a distinctly different colour

Hue familyblue

CSS keyword usableNo exact keyword

Colour harmonies

base +30°+90°+120°+180°+210°+240°+270°+330°

Complementary#403A00

Analogous#002640, #1A0040

Triadic#400006, #064000

Split complementary#401A00, #264000

Tetradic#400026, #403A00, #00401A

Tints, shades & saturation

+40%+30%+20%+10%base -10%-20%-30%-40%

Lighter +40%#0D24FF

Lighter +30%#0014D9

Lighter +20%#0010A6

Lighter +10%#000B73

Darker −10%#00010D

Darker −20%#000000

Darker −30%#000000

Darker −40%#000000

More saturated +25%#000640

Less saturated −25%#080D38

Channel breakdown

B64

Red0 (0%)

Green6 (2.4%)

Blue64 (25.1%)

Hue234.38°

Saturation (HSL)100%

Lightness12.55%

Dominant channelBlue

Hex per channelR 00 · G 06 · B 40

Keep nerding

Every link below is a page Nerdulator can generate from what it already knows about this value.

640

Number properties

Factors & divisors

Arithmetic

Representations

Nearest landmarks

Powers & multiples

Divisibility tests

Collatz (3n + 1) trajectory

As a percentage & fraction

Read another way

Keep nerding

Neighbouring numbers

Derived from 640

Nearby primes

Other readings

#000640 (colour)

Colour values

Brightness & contrast

Colour vision & accessibility

Named colours

Colour harmonies

Tints, shades & saturation

Channel breakdown

Keep nerding

Harmonies

Lighter and darker

Similar named colours

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