21 kilometers in centimeters

Conversion formula
How to convert 21 kilometers to centimeters?

We know (by definition) that: $1\mathrm{km}=100000\mathrm{cm}$

We can set up a proportion to solve for the number of centimeters.

Now, we cross multiply to solve for our unknown $x$:

Conclusion: 21 ⁢ km = 2100000 ⁢ cm

Conversion in the opposite direction

The inverse of the conversion factor is that 1 centimeter is equal to 4.76190476190476e-07 times 21 kilometers.

It can also be expressed as: 21 kilometers is equal to $\frac{1}{\mathrm{4.76190476190476e-07}}$ centimeters.

Approximation

An approximate numerical result would be: twenty-one kilometers is about two million, one hundred thousand centimeters, or alternatively, a centimeter is about zero times twenty-one kilometers.