XXI Roman Numerals
XXI in Roman Numerals can be written in numbers by combining the value of each Roman numeral, i.e., XXI = XX + I = 20 + 1 = 21. The higher Roman numerals precede the lower numerals resulting in the correct translation of XXI Roman Numerals. In this article, let us learn how to convert Roman numeral XXI into numbers and understand the value of XXI number in English.
XXI Meaning
The meaning of XXI in English in the numerical form can be expressed as 21 using the following method.
 XXI = XX + I
 XXI = 20 + 1
 XXI = 21
How to Write XXI Roman Numerals?
XXI in Numbers
The value of XXI in numbers can be found using the following methods.
XXI in Roman Numerals Translation
The numerical value of XXI Roman Numerals can be obtained by using any of the two methods given below:
Method 1: In this method, we break the Roman numerals into single letters, write the numerical value of each letter and add/subtract them.
 XXI = X + X + I = 10 + 10 + 1 = 21
Method 2: In this method, we consider the groups of Roman numerals for addition or subtraction such as,
 XXI = XX + I = 20 + 1 = 21
Therefore, the numerical value of XXI Roman numerals is 21.
☛ Also Check: Roman Numerals Calculator
What are the Basic Rules to Write Roman Numerals?
 When a bigger letter precedes a smaller letter, the letters are added. For example: CX, C > X, so CX = C + X = 100 + 10 = 110
 When a smaller letter precedes a bigger letter, the letters are subtracted. For example: IV, I < V, so IV = V  I = 5  1 = 4
 When a letter is repeated 2 or 3 times, they get added. For example: MM = M + M = 1000 + 1000 = 2000
 The same letter cannot be used more than three times in succession.
Numbers Related to XXI Roman Numerals
Roman numerals were used in ancient Rome and utilized combinations of letters using the Latin alphabets I, V, X, L, C, D, and M. It may seem different than numbers, but they are similar. For example, XXI Roman numerals are equivalent to the number 21. The roman numerals related to XXI are given below:
 XX = 20
 XXI = 20 + 1 = 21
 XXII = 20 + 2 = 22
 XXIII = 20 + 3 = 23
 XXIV = 20 + 4 = 24
 XXV = 20 + 5 = 25
 XXVI = 20 + 6 = 26
 XXVII = 20 + 7 = 27
 XXVIII = 20 + 8 = 28
 XXIX = 20 + 9 = 29
XXI Roman Numerals Examples

Example 1: Find the product of Roman Numerals XXI and LXXXIII.
Solution:
XXI = 20 + 1 = 21 and LXXXIII = 80 + 3 = 83
Now, XXI × LXXXIII = 21 × 83 = 1743
Since, MDCCXLIII = 1000 + 700 + 40 + 3 = 1743
Therefore, XXI × LXXXIII = MDCCXLIII 
Example 2: Find the sum of MXC and XXI Roman Numerals.
Solution:
MXC = 1000 + 90 = 1090 and XXI = 20 + 1 = 21
Now, MXC + XXI = 1090 + 21 = 1111
Since, MCXI = 1000 + 100 + 10 + 1 = 1111
Therefore, the sum of MXC and XXI Roman numerals is MCXI 
Example 3: Find the difference between XXI and VIII.
Solution:
Roman Numeral XXI is equal to 21 and VIII is 8.
Now, XXI  VIII = 21  8 = 13
Since, 13 = XIII
Therefore, XXI  VIII = XIII 
Example 4: Divide XXI by XV and find the quotient.
Solution:
The Roman numeral XXI is 21 and XV is 15.
When we divide XXI by XV, i.e., 21 ÷ 15, the quotient is 1.
Since, 1 = I
Therefore, XXI ÷ XV = I
FAQs on XXI Roman Numerals
What is XXI in Roman Numerals?
We will write XXI Roman numerals in the expanded form to determine its value. XXI = X + X + I = 10 + 10 + 1 = 21. Hence, the value of Roman Numerals XXI is 21.
Why is 21 Written in Roman Numerals as XXI?
We know that in Roman numerals, we write 1 as I, and 10 as X. Therefore, 21 in Roman numerals is written as XXI = XX + I = 20 + 1 = XXI.
What is the Remainder when XXI is Divided by XVIII?
We know that XXI = 21 and XVIII = 18 in numbers. On dividing 21 by 18, we get the quotient as 1 and it leaves a remainder of 3. Now, 3 = III. Therefore, when XXI is divided by XVIII, the remainder is III.
How is XXI Roman Numerals Written in Numbers?
To convert XXI Roman Numerals to numbers, the conversion involves breaking the Roman numerals on the basis of place values (ones, tens, hundreds, thousands), like this:
 Tens = 20 = XX
 Ones = 1 = I
 Number = 21 = XXI
What Should be Added to XXI Roman Number to Get MMMCMLXXXVIII?
First, we will write MMMCMLXXXVIII and XXI in numbers, i.e., XXI = 21 and MMMCMLXXXVIII = 3988. Now, 3988  21 = 3967. And, 3967 = MMMCMLXVII. Therefore, MMMCMLXVII should be added to 21 Roman numerals to get MMMCMLXXXVIII.
What is XXI in Hindu Arabic Numerals?
The value of XXI in Hindu Arabic numerals can be calculated using the following steps.
 We break the Roman numerals into single letters, write the numerical value of each letter and add or subtract them, as the case may be.
 In this case, XXI Roman number = X + X + I = 10 + 10 + 1 = 21
 Therefore, the value of XXI in Hindu Arabic numerals is 21.
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