d)+Prime+Numbers

What is the definition of a Prime Number? Posted by: **Craxyjosh** A Prime number is a number that can only be divided by one and itself. EX: 1, 3, 5.

Why isn't (for example) 4 a prime number? Posted by: **LemonMPie** The reason 4 isn't a prime number is because four can be divided by one, itself, and two. A prime number is a number that can only be divided by one and itself so if there's another number it can be divided by, it's not a prime number.

Posted by: CoconutCracker Also it isn't a prime number because it is an even number. All even numbers except for 2 are composite numbers.

What are some examples? Posted by: **Craxyjosh** Some examples of prime numbers are 1, 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, and 37.

What is the sieve of Eratosthenes? Posted by: **Craxyjosh** The Sieve of Eratosthenes is an ancient algorithm for finding prime numbers up to a specific number. Can anyone find an image that will help us understand what this is? Posted by: **Craxyjosh** < Easy to understand! How does the sieve of Eratosthenes work?- jchen727

Who was Eratosthenes? Posted by: **Craxyjosh** He was a Greek mathematician, poet, athlete, geographer and astronomer. Can anyone find a link to a web page that will give us more information about who Eratosthenes was and what he did. How about a picture of the man? Posted by: **Craxyjosh** http://en.wikipedia.org/wiki/Eratosthenes http://www-history.mcs.st-andrews.ac.uk/Biographies/Eratosthenes.html http://space.about.com/cs/astronomerbios/a/Eratosthenesbio.htm What is the opposite of a Prime Number? The opposite of a prime number is a composite number which can be divided by more than one number. Examples: 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22.

Posted by: **Partykala** 2 isn't a composite number it is a prime number because it can only be divided by 2 and 1 ?

Posted by: **Craxyjosh** A **composite number** is a positive integer which has a positive divisor other than one or itself. In other words, if 0 < n is an integer and there are integers 1 < a, b < n such that n = a × b then n is composite. By definition, every integer greater than one is either a prime number or a composite number. The number one is a unit - it is neither prime nor composite. For example, the integer 14 is a composite number because it can be factored as 2 × 7.

The fist 88 composite numbers are: 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30, 32, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 49, 50, 51, 52, 54, 55, 56, 57, 58, 60, 62, 63, 64, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 81, 82, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94, 95, 96, 98, 99, 100, 102, 104, 105, 106, 108, 110, 111, 112, 114, 115, 116, 117, 118, 119.

Posted by: SalinaKung A prime number is a whole number that only has two factors. Its factors are always one and the number itself. For example, the factors of 2 are 1 and 2. A composite number is a whole number that has more than two factors. For example, the factors of 6 are 3, 2, 1, and 6.