XXI Roman Numerals - How to Write XXI in Numbers

XXI Roman numerals may look like a group of letters, but they represent the number 21. Here, you understand the rules to convert the XXI Roman numeral into a number with solved examples. You will also learn fun facts related to Roman numerals to make learning even more interesting.

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What are Roman Numerals?

A long time ago, in ancient Rome, people didn’t use numbers like 1, 2, or 3. Instead, they used special letters to show numbers. These letters are called Roman numerals.

The Romans used certain letters from their alphabet to mean different amounts. Here is a simple table to help you understand:

Roman numerals were used for counting, writing dates, and even doing simple math. Today, we still see them on clocks, in books, and at big events. So whenever you spot letters like I, V, or X, remember you are looking at numbers from Roman times!

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What is XXI Roman Number?

XXI Roman number is a way of writing the number 21 using Roman numerals. It is made from three letters:

• X means 10

• Another X means another 10

• I mean 1

When you add them together:

10 + 10 + 1 = 21

So, the XXI Roman number represents the number 21 in Maths.

Read More: XXVII Roman Numerals

 How to Write XXI Roman Numerals in Numbers?

Now let’s learn how to write the number XXI  Roman numeral in numbers. To do this, we use the Roman letters that add up to 21.

Here’s an easy way to think about it:

Step 1: Start with the biggest Roman numeral you can use without going over 21. That’s X, which means 10.

Step 2: Use another X for another 10. Now you have 10 + 10, which is equal to 20.

Step 3: You still need 1 more to make 21, so you add I, which means 1.

Now put the letters together:

X + X + I = XXI

So, XXI in numbers is written as 21

It’s just like saying:

XXI = 21

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XXI in Roman Numeral Rules

Roman numerals follow special rules that help us understand what each group of letters means. Once you know the rules, reading and writing Roman numbers becomes much easier.

Here are the two most important rules to remember:

Rule 1: Add when the letters go from large to small

If a smaller number comes after a bigger one, you simply add the values.

For example:

XXI has the letters X, X, and I.

• The first X is 10

• The second X is another 10

• The I is 1

Since the numbers go from big to small (10, 10, then 1), we add them:

10 + 10 + 1 = 21

So, XXI means 21.

Rule 2: Subtract when the letters go from small to large

If a smaller number comes before a bigger one, you subtract the smaller number from the bigger one.

For example, IV has the letters I and V.

• I is 1

• V is 5

Since 1 comes before 5, we subtract:

5 - 1 = 4

 So, IV means 4.

Numbers Related to XXI Roman Numerals

Here are some Roman numerals that come just before and after XXI. These examples show how the numbers grow step by step:

• 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

Fun Facts About XXI Roman Numerals

Here are some facts about XXI Roman numerals:

• The number 21 is written as XXI in Roman numerals.

• You can see XXI on the faces of some old clocks.

• In the Olympics, Roman numerals are used to show the number of the games. For example, the 21st Olympics is written as Olympiad XXI.

• The Super Bowl often uses Roman numbers. Super Bowl 21 was written as Super Bowl XXI.

Read More: CMXX Roman Numeral

XXI Roman Numerals Solved Examples

Here are XXI Roman Numerals solved examples:

1. Compare XIX and XXI. Which is greater?

Solution:

The value of XIX = 10 + (10 - 1) = 19

The value of XXI = 10 + 10 + 1 = 21

Since the number 21 is more than the number 19, XXI is greater than XIX

2. What is the roman numeral for 15 + 6?

Solution: 15 + 6 = 21

Now write 21 in Roman numerals:

• X = 10

• X = 10

• I = 1

So, the answer is XXI

3. Subtract 5 from XXI. What is the answer in Roman numerals?

Solution:

First, find the value of XXI.

XXI = 10 + 10 + 1 = 21

Now subtract 5 from 21:

 21 - 5 = 16

Next, write 16 in Roman numerals:

10 = X

5 = V

1 = I

Put them together: X + V + I = XVI

4. What is XXI minus X?

Solution:

First, find the value of XXI:

XXI = 21

Now find the value of X:

X = 10

Subtract 21 - 10 = 11

Now write 11 in Roman numerals.

10 = X

1 = I

Put them together  X + I = XI

What do you get if you add V (5) to XVI (16)?

Solution:

First, find the value of each Roman numeral:

V = 5

XVI = 10 + 5 + 1 = 16

Now add them together:

5 + 16 = 21

Write 21 in Roman numerals:

10 = X

Another 10 = X

1 = I

Put them together. This gives XXI.

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