Perfect Numbers in Ruby
Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60  120 CE) classification scheme for natural numbers.
1  exercism fetch ruby perfectnumbers

Perfect Numbers
Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60  120 CE) classification scheme for natural numbers.
The Greek mathematician Nicomachus devised a classification scheme for natural numbers, identifying each as belonging uniquely to the categories of perfect, abundant, or deficient based on their aliquot sum. The aliquot sum is defined as the sum of the factors of a number not including the number itself. For example, the aliquot sum of 15 is (1 + 3 + 5) = 9

Perfect: aliquot sum = number
 6 is a perfect number because (1 + 2 + 3) = 6
 28 is a perfect number because (1 + 2 + 4 + 7 + 14) = 28

Abundant: aliquot sum > number
 12 is an abundant number because (1 + 2 + 3 + 4 + 6) = 16
 24 is an abundant number because (1 + 2 + 3 + 4 + 6 + 8 + 12) = 36

Deficient: aliquot sum < number
 8 is a deficient number because (1 + 2 + 4) = 7
 Prime numbers are deficient
Implement a way to determine whether a given number is perfect. Depending on your language track, you may also need to implement a way to determine whether a given number is abundant or deficient.
For installation and learning resources, refer to the exercism help page.
For running the tests provided, you will need the Minitest gem. Open a terminal window and run the following command to install minitest:
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gem install minitest

If you would like color output, you can require 'minitest/pride'
in
the test file, or note the alternative instruction, below, for running
the test file.
In order to run the test, you can run the test file from the exercise
directory. For example, if the test suite is called
hello_world_test.rb
, you can run the following command:
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ruby hello_world_test.rb

To include color from the command line:
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ruby r minitest/pride hello_world_test.rb

Source
Taken from Chapter 2 of Functional Thinking by Neal Ford. http://shop.oreilly.com/product/0636920029687.do
Submitting Incomplete Solutions
It's possible to submit an incomplete solution so you can see how others have completed the exercise.