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Recognised as Number

1,721

  • Positive
  • Odd
  • Prime
  • 4 digits

1,721 is an odd 4-digit integer and a prime number. It has 2 divisors and a digital root of 2.

Number properties

ParityOddnot divisible by 2
SignPositive
PrimalityPrime
Absolute value1,721
Digit count4
Digit sum11
Digit product14
Multiplicative persistence2times the digit product can be taken before one digit is left
Digital root2repeated digit sum
PalindromicNoreads differently backwards
Happy numberNosquared-digit sums reach 1
Harshad numberNodivisible by its own digit sum

Factors & divisors

Prime factorisation1,721
Distinct prime factors11,721
Number of divisors2
Sum of divisors σ(n)1,722
Aliquot sum1sum of the proper divisors
ClassificationDeficientthe aliquot sum is less than the number
Euler's totient φ(n)1,720integers below n that share no factor with it
Carmichael function λ(n)1,720the 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, 1,7212 in total

Arithmetic

Previous number1,720
Next number1,722
Double3,442
Half860.5
Square2,961,841
Cube5,097,328,361
Square root41.484937025≈irrational, shown to 9 decimal places
Cube root11.983774367≈
Negation-1,721
Reciprocal0.0005810575≈

Representations

Decimal1,721
Binary1101011100111 bits
Octal3271
Hexadecimal6B9
Base 361BT
Roman numeralMDCCXXI
In wordsone thousand, seven hundred and twenty-one
Ordinalone thousand, seven hundred and twenty-first
Scientific notation1.721 × 10^3
Engineering notation1.721 × 10^3

In other bases

Ternary2100202base 3; the most digit-efficient integer base after e: 7 digits
Quinary23341base 5; one hand: 5 digits
Septenary5006base 7: 4 digits
Nonary2322base 9; each digit is two ternary digits: 4 digits
Duodecimalbb5base 12; divides by 2, 3, 4 and 6, which is why eggs and inches come in twelves: 3 digits
Vigesimal461base 20; hands and feet, and the Mayan and Yoruba systems: 3 digits
Sexagesimal28:41base 60; Babylonian, and still how an hour and a circle are divided: 2 digits
Balanced ternary1T101T1Tdigits −1, 0 and +1 written T, 0 and 1; negation is swapping T and 1, so no sign is needed
Negabinary1101111001001base −2; place values alternate 1, −2, 4, −8, so every integer has exactly one form without a sign

Bit-level

0000011010111001
Bit length11 bitsto write the magnitude
Set bits7the population count, or Hamming weight
Zero bits4within that length
Bit parityodd7 set bits, so odd; not the same as the number itself being odd
Highest set bitbit 10worth 1,024
Lowest set bitbit 00 trailing zeros
Power of twoNo
Bytes206 b9
Gray code10111100101n XOR (n >> 1); successive values differ in exactly one bit

At each machine width

16-bit0000011010111001
32-bit00000000000000000000011010111001
64-bit0000000000000000000000000000000000000000000000000000011010111001
One's complement1111100101000110at 16 bits, every bit flipped
Bits reversed1001110101100000at 16 bits
Rotated left by 10000110101110010at 16 bits, wrapping
Shifted left by 1110101110010= 3,442, no wrap
Shifted right by 11101011100= 860, discarding the low bit
These bits as a double8.50286976 × 10^-321≈IEEE-754 binary64 reinterpretation of the same 64 bits (subnormal)

Nearest landmarks

Next prime1,723+2
Previous prime1,709−12
Distance to nearest prime0, it is prime
Nearest square below1,681
Nearest square above1,764

Powers & multiples

1,721 to the power 22,961,841
1,721 to the power 35,097,328,361
1,721 to the power 48,772,502,109,281
1,721 to the power 515,097,476,130,072,601
First ten multiples1,721, 3,442, 5,163, 6,884, 8,605, 10,326, 12,047, 13,768, 15,489, 17,210
Powers of twoBetween 2^10 (1,024) and 2^11 (2,048)

Divisibility tests

Divisible by 2No, remainder 1
Divisible by 3No, remainder 2
Divisible by 4No, remainder 1
Divisible by 5No, remainder 1
Divisible by 6No, remainder 5
Divisible by 7No, remainder 6
Divisible by 8No, remainder 1
Divisible by 9No, remainder 2
Divisible by 10No, remainder 1
Divisible by 11No, remainder 5
Divisible by 12No, remainder 5
Divisible by 100No, remainder 21

Collatz (3n + 1) trajectory

Steps to reach 155the total stopping time
Highest value reached5,8123× the starting value
Reaches 1Yesthe Collatz conjecture says every positive integer does, but it is unproven
First steps1,721 → 5,164 → 2,582 → 1,291 → 3,874 → 1,937 → 5,812 → 2,906 → 1,453 → 4,360 → …
Last steps… → 5 → 16 → 8 → 4 → 2 → 1

As a percentage & fraction

As a percentage172,100%
1,721% as a decimal17.21
1,721% of 1001,721
1,721% of 1,00017,210
As a fraction of 1001,721/100

Read another way

As seconds28 minutes and 41 seconds
As bytes1.681 KiB
As a year1721 AD
As a 24-bit colour#0006B9

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Neighbouring numbers

Nearby primes

Also reads as

1721 (year)

  • Common year
  • 365 days
  • 18th century
  • Ox

1721 was a common year of 365 days. It began on a Wednesday and ended on a Wednesday. Easter Sunday fell on 13 April.

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Structure of the year

Leap yearNonot divisible by 4
Days in the year365
Days in February28
1 January fell on aWednesday
31 December fell on aWednesday
Century18th century
Decade1720s
Chinese zodiacOx
Easter Sunday13 April

Patterns forced by the calendar

Weekday counts52 of each, plus an extra Wednesday365 days is 52 weeks and 1 day, and the remainder starts on the weekday 1 January falls on
Sundays52
Mondays52
Tuesdays52
Wednesdays53one of the extras
Thursdays52
Fridays52
Saturdays52
Friday the 13th1 of them13 June
ISO weeks52an ordinary 52-week year
Same calendar as1710the most recent year whose calendar is identical, so a printed one could be reused
Calendar repeats in1727, 1738, 17496 years later, then again after that; the gap is 6, 11 or 28 years, broken by centuries that skip a leap year

Months of 1721

January31 days, starts Wednesday
February28 days, starts Saturday
March31 days, starts Saturday
April30 days, starts Tuesday
May31 days, starts Thursday
June30 days, starts Sunday
July31 days, starts Tuesday
August31 days, starts Friday
September30 days, starts Monday
October31 days, starts Wednesday
November30 days, starts Saturday
December31 days, starts Monday

Time references

These values depend on today’s date and change daily.

Unix timestamp at the start-7,857,648,000
Unix timestamp at the end-7,826,112,001
Years from now305 years ago
Days from today111,654 days since 1 January

The number 1721

As a number1,721
In wordsone thousand, seven hundred and twenty-one
Roman numeralsMDCCXXI

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Neighbouring years

Also reads as

#117722 (colour)

  • #117722
  • Green
  • Dark
  • Nearest: Dark green

#117722 is a green with RGB values 17, 119, 34 and HSL 130°, 75%, 27%. It is a dark colour, so white text on it reaches 5.7:1 contrast (AA for normal text). The nearest named colour is Dark green.

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Colour values

#117722#117722
HEX#117722
HEX (short)#172
RGBrgb(17, 119, 34)
RGB (0–1)0.0667, 0.4667, 0.1333
RGB percentages6.7%, 46.7%, 13.3%
HSLhsl(130, 75%, 26.7%)
HSV / HSBhsv(130, 85.7%, 46.7%)
CMYK85.7%, 0%, 71.4%, 53.3%≈naive device-independent conversion; real print needs an ICC profile
24-bit integer1,144,610
CSS custom property--colour: #117722;

Brightness & contrast

Relative luminance0.13428WCAG 2.x, 0 is black and 1 is white
Perceived brightness92.4 of 255ITU-R BT.601 weighting
Light or darkDark
Best text colour on this backgroundWhitecontrast 5.7:1
Contrast with white5.7:1WCAG normal text: AA
Contrast with black3.69:1WCAG normal text: Fail
Greyscale equivalent#5B5B5B
Inverted#EE88DD

Colour vision & accessibility

Normal visionProtanopiaDeuteranopiaTritanopia
Protanopia#796B16no red cones; affects about 1% of men; ΔE 42.2 from the original
Deuteranopia#6E642Ano green cones; the most common form, about 1% of men; ΔE 41.5 from the original
Tritanopia#007466no blue cones; rare, and affects men and women equally; ΔE 40.1 from the original
Distinguishable without hueShifts in lightness toonever rely on hue alone to carry meaning
Contrast with white, large text5.7:1WCAG large text: AAA
Contrast with black, large text3.69:1WCAG large text: AA

Named colours

Dark green · ΔE 8.7Forest green · ΔE 11.3Green · ΔE 14.3Sea green · ΔE 20Olivedrab · ΔE 23.8Medium seagreen · ΔE 25.7
Nearest named CSS colourDark green (#006400)ΔE 8.65, clearly different but related
Hue familygreen
CSS keyword usableNo exact keyword

Colour harmonies

base+30°+90°+120°+180°+210°+240°+270°+330°
Complementary#771166
Analogous#337711, #117755
Triadic#221177, #772211
Split complementary#551177, #771133
Tetradic#113377, #771166, #775511

Tints, shades & saturation

+40%+30%+20%+10%base-10%-20%-30%-40%
Lighter +40%#6AEA80
Lighter +30%#3EE359
Lighter +20%#1ED03B
Lighter +10%#17A42F
Darker −10%#0B4A15
Darker −20%#041E09
Darker −30%#000000
Darker −40%#000000
More saturated +25%#008817
Less saturated −25%#22662D

Channel breakdown

R17
G119
B34
Red17 (6.7%)
Green119 (46.7%)
Blue34 (13.3%)
Hue130°
Saturation (HSL)75%
Lightness26.67%
Dominant channelGreen
Hex per channelR 11 · G 77 · B 22

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Every value on this page was computed from “1721” by Nerdulator’s number engine. Nothing here was retrieved from a database of answers or written by a model.