Prime numbers and composites
General · Mathematics
Study notes
Q: Classify 1, 2, 17, 21, 97 as prime/composite/neither. Is 91 prime? 1: neither! 2: prime (only even prime). 17: prime. 21 = 3×7: composite. 97: prime. 91 = 7×13: COMPOSITE (tricky! 91 = 7×13). Test divisibility up to √n: √91 ≈ 9.5, 7 divides it!