pi2r can be calculated, but is has no particular mathematical interpretation.
Pi x the diameter of the circle will hive you the circumference. The diameter is double the radius so the answer to your question is pi2r.
pi2rh + pi2r^2pi=most commonly 3.14r=radiush=heightr^2=radius squared
You would multiply the radius by two then multiply by pi which would be 3.14. Here would be the formula: C=pi2r C=circumference pi=3.14 when you round r=radius