21 deciliters in liters
Result
The conversion result is: 21 deciliters is equivalent to 2.1 liters.[1]
Conversion formula
How to convert 21 deciliters to liters?
We know (by definition) that: 1 dl ≈ 0.1 liter.
We can set up a proportion to solve for the number of liters.
1 dl / 21 dl ≈ 0.1 liter / x liter
Now, we cross multiply to solve for our unknown x:
x liter ≈ (21 dl / 1 dl) * 0.1 liter → x liter ≈ 2.1 liter
Conclusion:
21 dl ≈ 2.1 liter

Conversion in the opposite direction
The inverse of the conversion factor is that 1 liter is equal to 0.476190476190476 times 21 deciliters.
It can also be expressed as: 21 deciliters is equal to 1 / 0.476190476190476 liters.
Approximation
An approximate numerical result would be: twenty-one deciliters is about zero liters, or alternatively, a liter is about zero point four eight times twenty-one deciliters.
Footnotes
[1] The precision is 15 significant digits (fourteen digits to the right of the decimal point).
Results may contain small errors due to the use of floating point arithmetic.