Recognised as Number
1,021
- Positive
- Odd
- Prime
- 4 digits
1,021 is an odd 4-digit integer and a prime number. It has 2 divisors and a digital root of 4.
The canonical address for this page is /1021.
Number properties
ParityOddnot divisible by 2
SignPositive
PrimalityPrime
Absolute value1,021
Digit count4
Digit sum4
Digit product0zero, because one of the digits is zero
Multiplicative persistence1times the digit product can be taken before one digit is left
Digital root4repeated digit sum
PalindromicNoreads differently backwards
Happy numberNosquared-digit sums reach 1
Harshad numberNodivisible by its own digit sum
Factors & divisors
Prime factorisation1,021
Distinct prime factors11,021
Number of divisors2
Sum of divisors σ(n)1,022
Aliquot sum1sum of the proper divisors
ClassificationDeficientthe aliquot sum is less than the number
Euler's totient φ(n)1,020integers below n that share no factor with it
Carmichael function λ(n)1,020the smallest exponent with aˣ ≡ 1 for every unit coprime to n
Möbius function μ(n)−11 distinct prime factor, an odd number of them
SquarefreeYesno repeated prime factor
All divisors1, 1,0212 in total
Arithmetic
Representations
Decimal1,021
Binary111111110110 bits
Octal1775
Hexadecimal3FD
Base 36SD
Roman numeralMXXI
In wordsone thousand and twenty-one
Ordinalone thousand and twenty-first
Scientific notation1.021 × 10^3
Engineering notation1.021 × 10^3
In other bases
Ternary1101211base 3; the most digit-efficient integer base after e: 7 digits
Quinary13041base 5; one hand: 5 digits
Septenary2656base 7: 4 digits
Nonary1354base 9; each digit is two ternary digits: 4 digits
Duodecimal711base 12; divides by 2, 3, 4 and 6, which is why eggs and inches come in twelves: 3 digits
Vigesimal2b1base 20; hands and feet, and the Mayan and Yoruba systems: 3 digits
Sexagesimal17:1base 60; Babylonian, and still how an hour and a circle are divided: 2 digits
Balanced ternary111TT11digits −1, 0 and +1 written T, 0 and 1; negation is swapping T and 1, so no sign is needed
Negabinary10000001101base −2; place values alternate 1, −2, 4, −8, so every integer has exactly one form without a sign
Bit-level
0000001111111101
Bit length10 bitsto write the magnitude
Set bits9the population count, or Hamming weight
Zero bits1within that length
Bit parityodd9 set bits, so odd; not the same as the number itself being odd
Highest set bitbit 9worth 512
Lowest set bitbit 00 trailing zeros
Power of twoNo
Bytes203 fd
Gray code1000000011n XOR (n >> 1); successive values differ in exactly one bit
At each machine width
16-bit0000001111111101
32-bit00000000000000000000001111111101
64-bit0000000000000000000000000000000000000000000000000000001111111101
One's complement1111110000000010at 16 bits, every bit flipped
Bits reversed1011111111000000at 16 bits
Rotated left by 10000011111111010at 16 bits, wrapping
Shifted left by 111111111010= 2,042, no wrap
Shifted right by 1111111110= 510, discarding the low bit
These bits as a double5.04441024 × 10^-321≈IEEE-754 binary64 reinterpretation of the same 64 bits (subnormal)
Nearest landmarks
Powers & multiples
1,021 to the power 21,042,441
1,021 to the power 31,064,332,261
1,021 to the power 41,086,683,238,481
1,021 to the power 51,109,503,586,489,101
First ten multiples1,021, 2,042, 3,063, 4,084, 5,105, 6,126, 7,147, 8,168, 9,189, 10,210
Powers of twoBetween 2^9 (512) and 2^10 (1,024)
Divisibility tests
Divisible by 2No, remainder 1
Divisible by 3No, remainder 1
Divisible by 4No, remainder 1
Divisible by 5No, remainder 1
Divisible by 6No, remainder 1
Divisible by 7No, remainder 6
Divisible by 8No, remainder 5
Divisible by 9No, remainder 4
Divisible by 10No, remainder 1
Divisible by 11No, remainder 9
Divisible by 12No, remainder 1
Divisible by 100No, remainder 21
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 steps1,021 → 3,064 → 1,532 → 766 → 383 → 1,150 → 575 → 1,726 → 863 → 2,590 → …
Last steps… → 5 → 16 → 8 → 4 → 2 → 1
As a percentage & fraction
As a percentage102,100%
1,021% as a decimal10.21
1,021% of 1001,021
1,021% of 1,00010,210
As a fraction of 1001,021/100
Read another way
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Derived from 1,021
Also reads as
#001021 (colour)
- #001021
- Blue
- Dark
- Nearest: Black
#001021 is a blue with RGB values 0, 16, 33 and HSL 211°, 100%, 6%. It is a dark colour, so white text on it reaches 19.2:1 contrast (AAA for normal text). The nearest named colour is Black.
Colour values
#001021#001021
HEX#001021
RGBrgb(0, 16, 33)
RGB (0–1)0, 0.0627, 0.1294
RGB percentages0%, 6.3%, 12.9%
HSLhsl(210.9, 100%, 6.5%)
HSV / HSBhsv(210.9, 100%, 12.9%)
CMYK100%, 51.5%, 0%, 87.1%≈naive device-independent conversion; real print needs an ICC profile
24-bit integer4,129
CSS custom property--colour: #001021;
Brightness & contrast
Relative luminance0.0048WCAG 2.x, 0 is black and 1 is white
Perceived brightness16.6 of 255ITU-R BT.601 weighting
Light or darkDark
Best text colour on this backgroundWhitecontrast 19.16:1
Contrast with white19.16:1WCAG normal text: AAA
Contrast with black1.1:1WCAG normal text: Fail
Greyscale equivalent#0E0E0E
Inverted#FFEFDE
Colour vision & accessibility
Distinguishable without hueYesnever rely on hue alone to carry meaning
Contrast with white, large text19.16:1WCAG large text: AAA
Contrast with black, large text1.1:1WCAG large text: Fail
Named colours
Hue familyblue
CSS keyword usableNo exact keyword
Colour harmonies
Complementary#211100
Analogous#002121, #000021
Triadic#210010, #102100
Split complementary#210000, #212100
Tetradic#210021, #211100, #002100
Tints, shades & saturation
Channel breakdown
R0
G16
B33
Red0 (0%)
Green16 (6.3%)
Blue33 (12.9%)
Hue210.91°
Saturation (HSL)100%
Lightness6.47%
Dominant channelBlue
Hex per channelR 00 · G 10 · B 21
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Harmonies
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