# Convert number: 21 in Roman numerals, how to write?

## How to convert the Arabic number 21? 20 = ? ... 22 = ?

I = 1; X = 10;

### 2. Convert each subgroup:

20 = 10 + 10 = X + X = XX;
1 = I;

### 3. Wrap up the Roman numeral:

21 =
20 + 1 =
XX + I =
XXI;

#### XXI is a group of numerals in additive notation.

Additive notation = a group of two or more numerals, equal or sorted in descending order from high to low - to calculate the value add up the symbols. Additive notation of the Roman numerals
Subtractive notation = a group of two numerals, one of a lower value preceding another larger one, the only allowed ones are: IV, IX, XL, XC, CD, CM, M(V), M(X), (X)(L), (X)(C), (C)(D), (C)(M) - to calculate the value subtract the first symbol from the second. Subtractive notation of the Roman numerals

## Latest conversions of Arabic numbers to Roman numerals

 21 = XXI Mar 31 01:25 UTC (GMT) 53,445 = (L)MMMCDXLV Mar 31 01:25 UTC (GMT) 28,021 = (X)(X)(V)MMMXXI Mar 31 01:25 UTC (GMT) 278,678 = (C)(C)(L)(X)(X)(V)MMMDCLXXVIII Mar 31 01:25 UTC (GMT) 4,999 = M(V)CMXCIX Mar 31 01:25 UTC (GMT) 58,498 = (L)(V)MMMCDXCVIII Mar 31 01:25 UTC (GMT) 2,771,971 = (M)(M)(D)(C)(C)(L)(X)(X)MCMLXXI Mar 31 01:25 UTC (GMT) 2,000,078 = (M)(M)LXXVIII Mar 31 01:25 UTC (GMT) 0 = nulla - Romans did not have a numeral for zero; they were using the word: 'nulla'. Mar 31 01:25 UTC (GMT) 14,026 = (X)M(V)XXVI Mar 31 01:25 UTC (GMT) 17,471 = (X)(V)MMCDLXXI Mar 31 01:25 UTC (GMT) 18,382 = (X)(V)MMMCCCLXXXII Mar 31 01:25 UTC (GMT) 2,000,002 = (M)(M)II Mar 31 01:25 UTC (GMT) converted numbers, see more...

## The set of basic symbols of the Roman system of writing numerals

• ### (*) M = 1,000,000 or |M| = 1,000,000 (one million); see below why we prefer this notation: (M) = 1,000,000.

(*) These numbers were written with an overline (a bar above) or between two vertical lines. Instead, we prefer to write these larger numerals between brackets, ie: "(" and ")", because:

• 1) when compared to the overline - it is easier for the computer users to add brackets around a letter than to add the overline to it and
• 2) when compared to the vertical lines - it avoids any possible confusion between the vertical line "|" and the Roman numeral "I" (1).

(*) An overline (a bar over the symbol), two vertical lines or two brackets around the symbol indicate "1,000 times". See below...

Logic of the numerals written between brackets, ie: (L) = 50,000; the rule is that the initial numeral, in our case, L, was multiplied by 1,000: L = 50 => (L) = 50 × 1,000 = 50,000. Simple.

(*) At the beginning Romans did not use numbers larger than 3,999; as a result they had no symbols in their system for these larger numbers, they were added on later and for them various different notations were used, not necessarily the ones we've just seen above.

Thus, initially, the largest number that could be written using Roman numerals was:

• MMMCMXCIX = 3,999.