Number
40
- Positive
- Even
- Composite
- 2 digits
40 is an even 2-digit integer and a composite number. It has 8 divisors and a digital root of 4.
The canonical address for this page is /40.
Number properties
ParityEvendivisible by 2
SignPositive
PrimalityComposite
Absolute value40
Digit count2
Digit sum4
Digital root4repeated digit sum
PalindromicNoreads differently backwards
Happy numberNosquared-digit sums reach 1
Harshad numberYesdivisible by its own digit sum
Factors & divisors
Prime factorisation2^3 × 5
Distinct prime factors22, 5
Number of divisors8
Sum of divisors σ(n)90
Aliquot sum50sum of the proper divisors
ClassificationAbundantthe aliquot sum exceeds the number
Euler's totient φ(n)16integers below n that share no factor with it
SquarefreeNohas a repeated prime factor
All divisors1, 2, 4, 5, 8, 10, 20, 408 in total
Arithmetic
Representations
Decimal40
Binary1010006 bits
Octal50
Hexadecimal28
Base 3614
Roman numeralXL
In wordsforty
Ordinalfortieth
Scientific notation4 × 10^1
Engineering notation40
Nearest landmarks
Powers & multiples
40 to the power 21,600
40 to the power 364,000
40 to the power 42,560,000
40 to the power 5102,400,000
First ten multiples40, 80, 120, 160, 200, 240, 280, 320, 360, 400
Powers of twoBetween 2^5 (32) and 2^6 (64)
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 5
Divisible by 8Yes
Divisible by 9No, remainder 4
Divisible by 10Yes
Divisible by 11No, remainder 7
Divisible by 12No, remainder 4
Divisible by 100No, remainder 40
Collatz (3n + 1) trajectory
Steps to reach 18the total stopping time
Highest value reached40
Reaches 1Yesthe Collatz conjecture says every positive integer does, but it is unproven
First steps40 → 20 → 10 → 5 → 16 → 8 → 4 → 2 → 1
As a percentage & fraction
As a percentage4,000%
40% as a decimal0.4
40% of 10040
40% of 1,000400
As a fraction of 10040/100
Read another way
Keep nerding
Every link below is a page Nerdulator can generate from what it already knows about this value.
Derived from 40
Other readings
Also reads as
#000040 (colour)
- #000040
- Blue
- Dark
- Nearest: Midnight blue
#000040 is a blue with RGB values 0, 0, 64 and HSL 240°, 100%, 13%. It is a dark colour, so white text on it reaches 19.6:1 contrast (AAA for normal text). The nearest named colour is Midnight blue.
Colour values
#000040#000040
HEX#000040
RGBrgb(0, 0, 64)
RGB (0–1)0, 0, 0.251
RGB percentages0%, 0%, 25.1%
HSLhsl(240, 100%, 12.5%)
HSV / HSBhsv(240, 100%, 25.1%)
CMYK100%, 100%, 0%, 74.9%≈naive device-independent conversion; real print needs an ICC profile
24-bit integer64
CSS custom property--colour: #000040;
Brightness & contrast
Relative luminance0.0037WCAG 2.x, 0 is black and 1 is white
Perceived brightness21.6 of 255ITU-R BT.601 weighting
Light or darkDark
Best text colour on this backgroundWhitecontrast 19.55:1
Contrast with white19.55:1WCAG normal text: AAA
Contrast with black1.07:1WCAG normal text: Fail
Greyscale equivalent#050505
Inverted#FFFFBF
Colour vision & accessibility
Distinguishable without hueYesnever rely on hue alone to carry meaning
Contrast with white, large text19.55:1WCAG large text: AAA
Contrast with black, large text1.07:1WCAG large text: Fail
Named colours
Hue familyblue
CSS keyword usableNo exact keyword
Colour harmonies
Complementary#404000
Analogous#002040, #200040
Triadic#400000, #004000
Split complementary#402000, #204000
Tetradic#400020, #404000, #004020
Tints, shades & saturation
Channel breakdown
R0
G0
B64
Red0 (0%)
Green0 (0%)
Blue64 (25.1%)
Hue240°
Saturation (HSL)100%
Lightness12.55%
Dominant channelBlue
Hex per channelR 00 · G 00 · B 40
Keep nerding
Every link below is a page Nerdulator can generate from what it already knows about this value.
Harmonies
Similar named colours
Nerdulate something else
Nothing in mind? Surprise me · today’s page