#### Friendly Numbers

P
```/*
'In number theory, friendly numbers are two or more natural numbers with a common abundancy index, the
ratio between the sum of divisors of a number and the number itself.'
Source: https://en.wikipedia.org/wiki/Friendly_number
*/

export const FriendlyNumbers = (firstNumber, secondNumber) => {
// input: two integers
// output: true if the two integers are friendly numbers, false if they are not friendly numbers

// First, check that the parameters are valid
if (
!Number.isInteger(firstNumber) ||
!Number.isInteger(secondNumber) ||
firstNumber === 0 ||
secondNumber === 0 ||
firstNumber === secondNumber
) {
throw new Error('The two parameters must be distinct, non-null integers')
}

return abundancyIndex(firstNumber) === abundancyIndex(secondNumber)
}

function abundancyIndex(number) {
return sumDivisors(number) / number
}

function sumDivisors(number) {
let runningSumDivisors = number
for (let i = 0; i < number / 2; i++) {
if (Number.isInteger(number / i)) {
runningSumDivisors += i
}
}
return runningSumDivisors
}
```