Prime & Composite Numbers

  • 12= 3 x 4, Here 3 is a factor of 12, and 12 is a multiple  of 3.  4 is another factor of 12. In the same way, for 12, there are six factors in all. They are 1,2,3,4,6,12 as 12=1x12, 12=2x6, 12=3x4.
  • A number with exactly two factors-1 and itself is called a prime number. Example: 2 has only two factors -1 and 2. So, 2 is a prime number.
  • Prime Numbers between 100-200 are 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199.[21]
  • A number with at-least   three factors(more than two factors ) is called a Composite number. Example: 12 has six factors-1,2,3,4,6,12. So, 12 is a composite number.
  • 1 has only one factor. i.e. 1. So, 1 is neither a prime number nor a composite number.
  • Even Numbers  : Multiples of 2 or numbers divisible by 2 = {  2,4,6,8,10,.... }
  • Odd Numbers: numbers which are not multiples of 2 =  { 1,3,5,7,9,........ }
  • Sum of any two even numbers is an even number.
  • Sum of any two odd numbers is an even number
  • Sum of an even number and an odd number is an odd number.
Practice Questions -1  
1.The sum of all even numbers below 10 is .... 
2.The smallest even number formed by using the digits 1,2,3,4 and 5 is ......
3. Which of the following statement is correct.  [JNV 2019]
    A)Zero is an odd number  B) Zero is an even number  C) Zero is a prime number D) Zero is neither even nor odd number
4. The product of a non - zero whole number and its successor is always.... APTET July 2024
    1. an even number 2. an odd number 3. a prime number 4. a composite number  

Online Practice Test on Prime Numbers & Composite Numbers

Practice Questions - 2

  1. Highest(Largest/greatest )  two digit prime number is ...... [JNV 2013]
  2. Number of prime number’s below 10 is .........  [AP TET 2018]
  3. Which of the following statements is true?    
    1. All even numbers are  composite numbers
    2. All odd numbers are prime numbers 
    3. There are infinite  prime numbers 
    4. A prime number can be written as the product of more then  two (natural) numbers
  4. How many prime numbers are there between 100 and 200?  [CMAT 2017]
  5. If a and b are two positive integers such that a²-b²  =19, then the value  of  a is .... [SSC 2010 ]
    1. 9
    2. 10
    3. 20
    4. 20
  6. If x and y are two odd prime numbers such that x>y, then x² - y² is 
  1. an even number
  2. an odd number
  3. a prime number
  4. an odd prime number

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