21 mi to km conversion result above is displayed in three different forms: as a decimal (which could be rounded), in scientific notation (scientific form, standard index form or standard form in the United Kingdom) and as a fraction (exact result). Every display form has its own advantages and in different situations particular form is more convenient than another. For example usage of scientific notation when working with big numbers is recommended due to easier reading and comprehension. Usage of fractions is recommended when more precision is needed.
If we want to calculate how many Kilometers are 21 Miles we have to multiply 21 by 25146 and divide the product by 15625. So for 21 we have: (21 × 25146) ÷ 15625 = 528066 ÷ 15625 = 33.796224 Kilometers
So finally 21 mi = 33.796224 km
