e and pi...................throughout this.........curves and straight lines................2, 3 ...........how all primes start out............AND the only time ever..........that two primes are but a digit apart............2 and 3........is how e and pi start out.......................the respective numbers.............

Answer: 2π (or about 6.283 pieces of string).

Radians Preferred by Mathematicians

Because the radian is based on the pure idea of "the radius being laid along the circumference", it often gives simple and natural results when used in mathematics.