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2015-10-02T14:32:11+08:00

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Prime numbers are whole numbers that have 2 factors: only 1 and itself.
 
   Examples:
 
      · - 1 x 2 (2 factors)
      · - 1  x 3 (2 factors)
      · 23 - 1 x 23 (2 factors)

On the other hand, composite numbers are whole numbers that consist of more than 2 factors.
 
   Examples:
 
      · - 1 x 4, 2 x 2 (4 factors)
      · 6 - 1 x 6, 2 x 3 (4 factors)
      · 100 - 1 x 100, 2 x 50, 4 x 25, 5 x 20, 10 x 10 (9 factors)

Question: Is 15 a prime number?
 
   List down all the factors of 15 first so that we'll figure out if it's a prime number.
 
   15 = 1 x 15, 3 x 5 (4 factors)
 
    It has 4 factors. Does it mean that it's a prime number?
 
   NO, because as I've said earlier, prime numbers have only 2 factors but it's stated above that 15 has 4 factors.
 
   15 is a composite number.

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Have a wondrous day =)
0
2015-10-02T21:01:24+08:00
No.It's factors are 5 and 3.So the prime numbers are the numbers with two factors like 7 it's only factors is only 7 and 1. So that 15 is not a prime number it belongs to composite numbers.
 TRIVIA:    
        Do you know that Prime numbers and odd numbers are different.
1 5 1
Actually, it's not trivial :-)
just joke