Eratostenes and Prime Numbers

ERATOSTENES

Eratosthenes was a Greek mathematician from the third century BC (before Christ).  He was also a geographer, poet, astronomer, philosopher and athlete.  He was the first person to calculate the circumference of the Earth and the distance between the Earth and the Sun.  Latitude and longitude were also invented by him and were used to create the first map of the world (that used these measurements). 

Eratosthenes also proposed a simple algorithm for finding prime numbers known in mathematics as the “Sieve of Eratosthenes.” Later in his life he was put in charge of the Library of Alexandria , the center of science and learning in the ancient world, and was good friends with Archimedes.  By 194 BC he had lost his sight and it is said that he let himself die of starvation at the age of 80 in Alexandria, Egypt. 

PRIME NUMBERS

In Mathematics, a prime number is a natural number greater than 1 that has only 2 different divisors: the same number and 1. On the other hand composite numbers that are those who have another natural divisor apart from the same number and 1. The prime numbers less than 100 are the following: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89,and 97. This conclusion was reached through the“Eratostenes Sieve.”

The property of being a prime number is called primality (primalidad).

Sometimes the number 1 is considered to be a prime number, however some authors don´t consider it as a prime number because it only has one divisor: 1.

We can consider that the prime numbers are the bricks with which we can build any natural number. For example we can write the number 23,244 as the product of 2²· 3· 13· 149.

In the decimal system all the prime numbers except 2 and 5 finish in 1, 3, 7, or 9.

Homework: I want you to tell me in the next lesson the main ideas in this text. Don't translate, please