Read and Write Roman Numeral XXI

Roman numeral symbols are written and read from left to right, from highest to lowest values. If XXI is text, it is the number 21.

Miscellaneous & Conversions For 21

Written EnglishTwenty-One
Roman Numeral 21XXI
RGB Colour (# 015 or #000015)
 
 

Decimal / Number21
Binary10101
Ternary210
Hexadecimal (Hex)0x15
Quaternary111
Quinary41
Senary (Heximal)33
Octal25
Duodecimal (Dozenal)19

Mathematics

Prime Factors: 3 x 7 = 21
Factorial: 21!5.10909421717E+19
Harshad Number: 21 True
Triangular Number Of 21 231
Square Root: √21 4.58257569496
Cube Root (Root 3): 3√21 2.75892417638
Tesseract Root (Root 4): 4√21 2.14069514293
Quintal / nth Root. (Root 5) 5√21 1.83841628725
¾ Root9.80989753229
Fibonnaci # 21 10946
Recipricol 1/ 21 0.047619047619
Quarter 1/45.25 or 5.25/21
Half 1/210.50 or 10.50/21
Third 1/37 or 7/21

Roman Numeral Chart. Read & Write 21

Reading and writing roman numerals isn't common knowledge. However, this roman numeral chart should help you read and write numbers in roman numerals from 1 to 1,000,000. Using an overline symbol is times 1,000. ( Example: X means to add 3 zeros to your number. So X which is 5, but written as X with the overline is 5,000.

  • When a symbol appears after a larger symbol it is added: Example: VI = V + I = 5 + 1 = 6
  • When a symbol appears before a larger symbol it is subtracted: Example: IX = X - I = 10 - 1 = 9
  • Do not use the same symbol more than 3 times. But, IIII is sometimes used for 4
1 I 10 x 500 D 1,001 MI
2 II 20 XX 501 DI 1,002 MII
3 III 30 XXX 530 DXXX 1,030 MXXX
4 IV 40 XL 550 DL 1,550 MDL
5 V 50 L 600 DC 1,555 MDLV
6 VI 60 LX 650 DCL 5,000 V
7 VII 70 LXX 700 DCC 10,000 X
8 VIII 80 LXXX 800 DCCC 50,000 L
9 IX 90 XC 890 DCCCXC 100,000 C
10 X 95 XCV 900 CM 500,000 D
11 XI 99 XCIX 950 CML 1,000,000 M
12 XII... 100 C 1000 M    
Most requested roman numerals
39 XXXIX
37 XXXVII

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