Recognised as Number
999
- Positive
- Odd
- Composite
- 3 digits
999 is an odd 3-digit integer and a composite number. It has 8 divisors and a digital root of 9.
Number properties
ParityOddnot divisible by 2
SignPositive
PrimalityComposite
Absolute value999
Digit count3
Digit sum27
Digit product729
Multiplicative persistence4times the digit product can be taken before one digit is left
Digital root9repeated digit sum
PalindromicYesreads the same backwards
Happy numberNosquared-digit sums reach 1
Harshad numberYesdivisible by its own digit sum
Factors & divisors
Prime factorisation3^3 × 37
Distinct prime factors23, 37
Number of divisors8
Sum of divisors σ(n)1,520
Aliquot sum521sum of the proper divisors
ClassificationDeficientthe aliquot sum is less than the number
Euler's totient φ(n)648integers below n that share no factor with it
Carmichael function λ(n)36the smallest exponent with aˣ ≡ 1 for every unit; smaller than φ(n) = 648
Möbius function μ(n)0zero, because a prime divides n twice
SquarefreeNohas a repeated prime factor
All divisors1, 3, 9, 27, 37, 111, 333, 9998 in total
Arithmetic
Representations
Decimal999
Binary111110011110 bits
Octal1747
Hexadecimal3E7
Base 36RR
Roman numeralCMXCIX
In wordsnine hundred and ninety-nine
Ordinalnine hundred and ninety-ninth
Scientific notation9.99 × 10^2
Engineering notation999
In other bases
Ternary1101000base 3; the most digit-efficient integer base after e: 7 digits
Quinary12444base 5; one hand: 5 digits
Septenary2625base 7: 4 digits
Nonary1330base 9; each digit is two ternary digits: 4 digits
Duodecimal6b3base 12; divides by 2, 3, 4 and 6, which is why eggs and inches come in twelves: 3 digits
Vigesimal29jbase 20; hands and feet, and the Mayan and Yoruba systems: 3 digits
Sexagesimal16:39base 60; Babylonian, and still how an hour and a circle are divided: 2 digits
Balanced ternary1101000digits −1, 0 and +1 written T, 0 and 1; negation is swapping T and 1, so no sign is needed
Negabinary10000111011base −2; place values alternate 1, −2, 4, −8, so every integer has exactly one form without a sign
Bit-level
0000001111100111
Bit length10 bitsto write the magnitude
Set bits8the population count, or Hamming weight
Zero bits2within that length
Bit parityeven8 set bits, so even; not the same as the number itself being odd
Highest set bitbit 9worth 512
Lowest set bitbit 00 trailing zeros
Power of twoNo
Bytes203 e7
Gray code1000010100n XOR (n >> 1); successive values differ in exactly one bit
At each machine width
16-bit0000001111100111
32-bit00000000000000000000001111100111
64-bit0000000000000000000000000000000000000000000000000000001111100111
One's complement1111110000011000at 16 bits, every bit flipped
Bits reversed1110011111000000at 16 bits
Rotated left by 10000011111001110at 16 bits, wrapping
Shifted left by 111111001110= 1,998, no wrap
Shifted right by 1111110011= 499, discarding the low bit
These bits as a double4.9357158 × 10^-321≈IEEE-754 binary64 reinterpretation of the same 64 bits (subnormal)
Nearest landmarks
Powers & multiples
999 to the power 2998,001
999 to the power 3997,002,999
999 to the power 4996,005,996,001
999 to the power 5995,009,990,004,999
First ten multiples999, 1,998, 2,997, 3,996, 4,995, 5,994, 6,993, 7,992, 8,991, 9,990
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 3
Divisible by 5No, remainder 4
Divisible by 6No, remainder 3
Divisible by 7No, remainder 5
Divisible by 8No, remainder 7
Divisible by 9Yes
Divisible by 10No, remainder 9
Divisible by 11No, remainder 9
Divisible by 12No, remainder 3
Divisible by 100No, remainder 99
Collatz (3n + 1) trajectory
Steps to reach 149the total stopping time
Reaches 1Yesthe Collatz conjecture says every positive integer does, but it is unproven
First steps999 → 2,998 → 1,499 → 4,498 → 2,249 → 6,748 → 3,374 → 1,687 → 5,062 → 2,531 → …
Last steps… → 5 → 16 → 8 → 4 → 2 → 1
As a percentage & fraction
As a percentage99,900%
999% as a decimal9.99
999% of 100999
999% of 1,0009,990
As a fraction of 100999/100
Read another way
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Derived from 999
Other readings
Also reads as
#999999 (colour)
- #999999
- Grey
- Dark
- Nearest: Dark grey
#999999 is a grey with RGB values 153, 153, 153 and HSL 0°, 0%, 60%. It is a dark colour, so black text on it reaches 7.4:1 contrast (AAA for normal text). The nearest named colour is Dark grey.
Colour values
#999999#999999
HEX#999999
HEX (short)#999
RGBrgb(153, 153, 153)
RGB (0–1)0.6, 0.6, 0.6
RGB percentages60%, 60%, 60%
HSLhsl(0, 0%, 60%)
HSV / HSBhsv(0, 0%, 60%)
CMYK0%, 0%, 0%, 40%≈naive device-independent conversion; real print needs an ICC profile
24-bit integer10,066,329
CSS custom property--colour: #999999;
Brightness & contrast
Relative luminance0.31855WCAG 2.x, 0 is black and 1 is white
Perceived brightness153 of 255ITU-R BT.601 weighting
Light or darkDark
Best text colour on this backgroundBlackcontrast 7.37:1
Contrast with white2.85:1WCAG normal text: Fail
Contrast with black7.37:1WCAG normal text: AAA
Greyscale equivalent#999999
Inverted#666666
Colour vision & accessibility
Distinguishable without hueYesnever rely on hue alone to carry meaning
Contrast with white, large text2.85:1WCAG large text: Fail
Contrast with black, large text7.37:1WCAG large text: AAA
Named colours
Hue familygrey
CSS keyword usableNo exact keyword
Colour harmonies
Complementary#999999
Analogous#999999, #999999
Triadic#999999, #999999
Split complementary#999999, #999999
Tetradic#999999, #999999, #999999
Tints, shades & saturation
Channel breakdown
R153
G153
B153
Red153 (60%)
Green153 (60%)
Blue153 (60%)
Hue0°
Saturation (HSL)0%
Lightness60%
Dominant channelNone: the channels are equal (a neutral grey)
Hex per channelR 99 · G 99 · B 99
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