Perfect and amicable numbers
General · Mathematics
Study notes
Q: Show 28 is perfect and check 220, 284 are amicable. Divisors of 28: 1,2,4,7,14. Sum: 1+2+4+7+14 = 28 ✓ PERFECT! 28 = 2²(2³-1) = 4×7: Euclid's form with p = 3! 220: divisors sum: 1+2+4+5+10+11+20+22+44+55+110 = 284. 284: 1+2+4+71+142 = 220. Amicable ✓ (Pythagoras knew!)