The Math Meridian
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Prime and composite numbers

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Learn it A prime number has exactly two factors: 1 and itself. A composite number has more than two. 1 is neither.

Example: Is 91 prime or composite?

  1. Try small primes: 2 (no, odd), 3 (9 + 1 = 10, no), 5 (no), 7: $91 \div 7 = 13$.
  2. 91 has factors 1, 7, 13, 91.
  3. So 91 is composite.

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