220 and 284 (Amicable Numbers) - Numberphile
Why do 220 and 284 get along so well? Dr James Grime introduces us to the world of so-called amicable numbers. More links & stuff in full description below ↓↓↓ James has his own website...
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JAMES GRIME: One, two, three, test, test, test. BRADY HARAN: You know that's not your-- JAMES GRIME: OK. Hello everyone, how are you doing? OK, so today, we're not going to do a number by itself, but a number that comes with a friend-- 220 and 284. These are called amicable numbers, or friendly numbers. OK, so why are two numbers friends? Well, we're going to look at the divisors of these numbers. So what divides 220? Well, 1 divides 220. 2, 4, 5, 10, 11, 20, 22, 44, 55, 110, and 220 itself, but we don't include 220 itself, not the number itself. So we take these numbers here. And if we add them up, we're going to get 284. But if we do the same thing for 284, what divides 284? 1, 2, 4, 71 divides, and 142. If we take those nu...
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JAMES GRIME: One, two, three, test, test, test. BRADY HARAN: You know that's not your-- JAMES GRIME: OK. Hello everyone, how are you doing? OK, so today, we're not going to do a number by itself, but a number that comes with a friend-- 220 and 284. These are called amicable numbers, or friendly numbers. OK, so why are two numbers friends? Well, we're going to look at the divisors of these numbers. So what divides 220? Well, 1 divides 220. 2, 4, 5, 10, 11, 20, 22, 44, 55, 110, and 220 itself, but we don't include 220 itself, not the number itself. So we take these numbers here. And if we add them up, we're going to get 284. But if we do the same thing for 284, what divides 284? 1, 2, 4, 71 divides, and 142. If we take those nu...
