Which of the following is a prime number?
- A.81
- B.83 ✓
- C.85
- D.87
Explanation: 83 has no factors other than 1 and itself, so it is prime; the other options can all be divided evenly by a smaller number.
Class 6 IMO Mathematics Olympiad practice · Number Sense · Factors, Multiples & Primes
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