Roman Numerals

Roman Numerals: 21 = XXI

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 limitations 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

 2024-08-13 20:23:53 MMXXIV-VIII-XIII XX:XXIII:LIII

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

The chemical element with atomic number 21 is Scandium (Sc).

Numbers close to 21

Below are the numbers 18 through 24, which are close to 21. 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

Roman numerals originate, as the name suggests, from the Ancient Roman empire. Unlike our position based system with base 10, the roman system is based on addition (and sometimes subtraction) of seven different values. These are symbols used to represent these values:

 Symbol Value I 1 V 5 X 10 L 50 C 100 D 500 M 1000

For example, to express the number 737 in roman numerals you write DCCXXXVII, that is 500 + 100 + 100 + 10 + 10 + 10 + 5 + 1 + 1. However, for the numbers 4 and 9, subtraction is used instead of addition, and the smaller number is written in front of the greater number: e.g. 14 is written as XIV, i.e. 10 + 5 − 1, and 199 is expressed as CXCIX i.e. 100 + 100 − 10 + 10 − 1. It could be argued that 199 would be more easily written as CIC, but according to the most common definition you can only subtract a number that is one order of magnitude smaller than the numbers you're subtracting from, meaning that IC for 99 is incorrect.

Roman numerals are often used in numbered lists, on buildings to state the year they were built, and in names of regents, such as Louis XVI of France.

Feel free to link to this site if you find it useful. It's also possible to link directly to specific numbers, such as roman-numerals.info/XXXVII or roman-numerals.info/37. You can also link to intervals, for instance roman-numerals.info/1-100 or roman-numerals.info/1980-2020, to see the numbers in a list format.