A problem by Shakil Ahmed

Level pending

Which one is a perfect number?

28 21 29 25

Shakil Ahmed by Shakil Ahmed , 29, Bangladesh

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2 solutions

Mehul Arora
Jan 8, 2015

A perfect number is one which is half the sum of all it's factors.

Hence the answer is 28.

1 Helpful 0 Interesting 0 Brilliant 0 Confused
Brock Brown
Jan 8, 2015 
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def divisors(x):
    answers = []
    n = 1
    while n < x:
        if x % n == 0:
            answers.append(n)
        n += 1
    return answers
def perfect(x):
    return x == sum(divisors(x))
for i in (29, 25, 21, 28):
    if perfect(i):
        print "Answer:", i

0 Helpful 0 Interesting 0 Brilliant 0 Confused

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