A prime number is a whole number which only has two factors: one and itself. A prime number is a whole number which only has two factors: one and itself. For example: 13 …since only 1 and 13 can evenly divide into 13 For example: 13 …since only 1 and 13 can evenly divide into 13

The numbers 0 and 1 are neither prime nor composite. The numbers 0 and 1 are neither prime nor composite.

A Composite number has one or more factors in addition to one and itself. A Composite number has one or more factors in addition to one and itself. For Example: 10…since 1, 2, 5, and 10 evenly divide into 10. For Example: 10…since 1, 2, 5, and 10 evenly divide into 10.

All even numbers are divisible by two and so all even numbers greater than two are Composite numbers. All even numbers are divisible by two and so all even numbers greater than two are Composite numbers. 2 is the ONLY EVEN Prime Number 2 is the ONLY EVEN Prime Number

Eratosthenes ( B.C., Greece) devised a 'sieve' to discover prime numbers. A sieve is like a strainer that you use to drain spaghetti when it is done cooking. The water drains out, leaving your spaghetti behind. Eratosthenes's sieve drains out composite numbers and leaves prime numbers behind. Eratosthenes ( B.C., Greece) devised a 'sieve' to discover prime numbers. A sieve is like a strainer that you use to drain spaghetti when it is done cooking. The water drains out, leaving your spaghetti behind. Eratosthenes's sieve drains out composite numbers and leaves prime numbers behind.

To use the sieve of Eratosthenes to find the prime numbers up to 100, make a chart of the first one hundred positive integers (1- 100): To use the sieve of Eratosthenes to find the prime numbers up to 100, make a chart of the first one hundred positive integers (1- 100):

Cross out 1, because it is not Prime. Cross out 1, because it is not Prime.

Circle 2, because it is the smallest positive even prime. Now cross out every multiple of 2; in other words, cross out every second number. Circle 2, because it is the smallest positive even prime. Now cross out every multiple of 2; in other words, cross out every second number.

Circle 3, the next Prime. Then cross out all of the multiples of 3; in other words, every third number. Some, like 6, may have already been crossed out because they are multiples of 2. Circle 3, the next Prime. Then cross out all of the multiples of 3; in other words, every third number. Some, like 6, may have already been crossed out because they are multiples of 2.

Circle the next open number, 5. Now cross out all of the multiples of 5, or every 5th number. Circle the next open number, 5. Now cross out all of the multiples of 5, or every 5th number.

Continue doing this until all the numbers through 100 have either been circled or crossed out. You have just circled all the prime numbers from 1 to 100! Continue doing this until all the numbers through 100 have either been circled or crossed out. You have just circled all the prime numbers from 1 to 100!

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. 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.

You could use The Sieve of Erathosthenes to find all the prime numbers, as far as you can count! You could use The Sieve of Erathosthenes to find all the prime numbers, as far as you can count!

FOXNEWS.COM HOME > SCITECH FOXNEWS.COM HOME > SCITECH UCLA Mathematicians Discover 13-Million- Digit Prime Number UCLA Mathematicians Discover 13-Million- Digit Prime Number Saturday, September 27, 2008 Saturday, September 27, 2008 LOS ANGELES — Mathematicians at UCLA have discovered a 13-million-digit prime number, a long-sought milestone that makes them eligible for a $100,000 prize. LOS ANGELES — Mathematicians at UCLA have discovered a 13-million-digit prime number, a long-sought milestone that makes them eligible for a $100,000 prize.