For 10 points—name this Greek who also devised a namesake "sieve"for identifying prime numbers.
Upon the death of his teacher Callimachus in 240 BCE, this man became the third librarian at Alexandria. His Platonicus dealt with the mathematics that underlie Plato's philosophy, though it is two other works, Introduction to Arithmetic and On the Measurement of the Earth, that contain his famous approximation of the circumference of the earth at 250,000 stadia. For 10 points—name this Greek who also devised a namesake "sieve"for identifying prime numbers.
Upon the death of his teacher Callimachus in 240 BCE, this man became the third librarian at Alexandria.
{Eratosthenes} of Cyrene