What is friendly numbers

Hello,

6 and 28 are friendly numbers.

1) calculate the divisors of each numbers:

div 6={1,2,3,6} sum=1+2+3+6=12 divide by the number: 12/6=2.

div 28={1,2,4,7,14,28} sum=1+2+4+7+28=56 = = >56/28=2

Ratio fo the sum of divisors by the number are the same: these are friendly numbers.

ex: (6,28), (30,140), (80,20), (40,224), (12,234), (84,270) ...