Roman Numerals

# Roman Numerals: XXI = 21

## Convert Roman Numerals

Arabic numerals:
Roman numerals:
 Arabicnumerals 0 1 M C X I 2 MM CC XX II 3 MMM CCC XXX III 4 CD XL IV 5 D L V 6 DC LX VI 7 DCC LXX VII 8 DCCC LXXX VIII 9 CM XC IX

The converter lets you go from arabic to roman numerals and vice versa. Simply type in the number you would like to convert in the field you would like to convert from, and the number in the other format will appear in the other field. Due to the limitions of the roman number system you can only convert numbers from 1 to 3999.

To easily convert between roman and arabic numerals you can use the table above. The key is to handle one arabic digit at a time, and translate it to the right roman number, where zeroes become empty. Go ahead and use the converter and observe how the table shows the solution in realtime!

## Current date and time in Roman Numerals

 2018-07-21 09:15:24 MMXVIII-VII-XXI IX:XV:XXIV

Here is the current date and time written in roman numerals. Since the roman number system doesn't have a zero, the hour, minute, and second component of the timestamps sometimes become empty.

## The year 21

Here you can read more about what happened in the year 21.

## The number 21

The number 21 is divisble by 3 and 7 and can be prime factorized into 3×7.

21 as a binary number: 10101
21 as an octal number: 25
21 as a hexadecimal number: 15

## Numbers close to XXI

Below are the numbers XVIII through XXIV, which are close to XXI. The right column shows how each roman numeral adds up to the total.

 18 = XVIII = 10 + 5 + 1 + 1 + 1 19 = XIX = 10 + 10 − 1 20 = XX = 10 + 10 21 = XXI = 10 + 10 + 1 22 = XXII = 10 + 10 + 1 + 1 23 = XXIII = 10 + 10 + 1 + 1 + 1 24 = XXIV = 10 + 10 + 5 − 1