NCERT Exemplar Solutions
Class 6 - Mathematics - Unit 1: Number System - Fill in the Blanks

Question 140

Idea: A factor of a number is a whole number that divides it exactly (no remainder).

Definition: If a number has more than two factors, it is called a composite number.

Examples:

• For 4:
  \(\text{Factors of }4=\{1,2,4\}\)
  \(\text{Number of factors}=3\)
  \(3>2\Rightarrow 4\) is composite.
• For 6:
  \(\text{Factors of }6=\{1,2,3,6\}\)
  \(\text{Number of factors}=4\)
  \(4>2\Rightarrow 6\) is composite.
• For 8:
  \(\text{Factors of }8=\{1,2,4,8\}\)
  \(\text{Number of factors}=4\)
  \(4>2\Rightarrow 8\) is composite.

Compare: A prime number has exactly two factors (1 and itself).
Example: \(\text{Factors of }5=\{1,5\}\) → two factors → 5 is not composite.

Special case: \(1\) has only one factor (\(1\) itself), so it is neither prime nor composite.