Eratosthenes is best known as a famous ancient Greek mathematician. In addition, he was an outstanding geographer, astronomer, and historian. Contemporaries nicknamed him "beta", after the second letter of the Greek alphabet, because he proved himself the second‑best scholar in practically every field. Eratosthenes was born in the city of Cyrene in Greece (now Libya in North Africa) in 276 BC. In his youth he studied in Athens. Eventually he made a name for himself in many scientific domains, which attracted the attention of the Egyptian ruler Ptolemy III. Ptolemy invited Eratosthenes to Alexandria so that he could educate his son and become the chief librarian of the great Library of Alexandria. It is believed that he died of starvation in 195 BC after becoming blind and unable to work. One of his major achievements in mathematics is the creation of a sieve that identifies prime numbers up to any given limit. This sieve, called the Sieve of Eratosthenes, remains important today and is used in number theory. Prime numbers are natural numbers greater than 1 that are divisible only by themselves and by 1. Eratosthenes realized that if you write all natural numbers starting from 2 onward and eliminate all multiples of 2, then move to the next available number (3) and eliminate all its multiples, and continue this process, you eventually obtain the list of prime numbers.
