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How to Check Whether a Number is Perfect Number or Not in Python – GATE, Interview & Placement
Jun 1, 2025
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0:00
uh hello guys uh welcome to this video
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So in this video I will show you a
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Python program which is asked commonly
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inside uh interviews for programming or
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competitive exams or placements
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uh whether to check whether a number is
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a perfect number or
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not So it is commonly asked So first of
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all I will show you what is actually a
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perfect number So in mathematics perfect
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number is that number which is uh let me
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show you this is actually the python
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program So
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python app 8 as I run the program it
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will ask you to enter a particular
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number and if I just say 16 So I write
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16 here So you will see 16 is not a
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perfect number So first of all uh if you
0:48
google it what is perfect
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number so perfect number is a positive
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integer whose the sum of its proper
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divisor excluding the number itself
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equals the number itself So what do you
1:00
mean by that
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so it is a number for example 6 is a
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perfect number because it's proper
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divisor such as 6 is divisible by
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1 It's divisible by 2 2 3's are six and
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it's also divisible by 3 So if you sum
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all these numbers which is 1 + 2 + 3 it
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comes out to be six So that is the
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definition of a perfect number So if I
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just input this number in this program
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if I say six you will see six is a
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perfect
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number because the sum of all the
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divisors excluding the number itself So
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six is not included in this So it
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basically comes in the table of 1 2 and
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then three So 32 + 5 is equal to
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6 So in this
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way so we actually
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uh written this program here So now let
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me show you step by step
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uh just using this Python tutor website
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where you can visualize the program step
2:10
by step So here the very first step here
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you need to provide the number So if I
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provide six here you will see the global
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variable has been created The number has
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six variable So this variable is created
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It has holding the value of
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six And now for detecting whether this
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number is a perfect number or not We
2:31
need some variables So we declared this
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variable sum of divisor to keep track of
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the sum Initially the value is zero So
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another variable is created sum of
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divisor is zero And now we run a simple
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for loop for i in range 1 to the number
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So number is not included here So it
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will run until 1 to 5 So because the
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actual number is not included right here
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So it will run up
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till 6 - 1 So it will run up to five and
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it will there is the simple condition
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right put here We are simply checking
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that if the remainder comes out to be
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zero So we are simply checking if
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one So for the very first thing I will
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be one Here you can see I So we are
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simply checking that if six is divisible
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by one So as you can see it is divisible
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So remainder comes out to be zero So
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this condition will evaluates to
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true and then this one will be added to
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this sum of divisor So this will this
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value will change from 0 to
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1 So now it will iterate to the next
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condition here It will now I will become
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two Again it will check 6 is divisible
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by two Again it will add this come to
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this and 1 + 2 it will become
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three So you can see that now it will
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move to the next iteration So I will be
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now three Three again is divisible by 6
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It will come out Remainder is zero So
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again three will be added from here 3 +
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3
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6 So now sum of divisor becomes six Now
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four is
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not 6 is not divisible by four So
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condition will be false It will move to
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five Five is not divisible by six So now
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as soon as I reaches six so the loop
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will end And then we'll simply compare
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that if this variable is equal to the
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number itself then this is actually a
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perfect number So we print out this
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result six is a perfect
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number And now let's suppose if I take
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uh a
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[Music]
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example a number which is not
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divisible Let's suppose I
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take four as example So I taken
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four So again we'll be checking
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here I will be one So I is four is
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divisible by one So sum of divisor one
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will be added Now two 2 is also
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divisible So
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two will be added to this variable So 2
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+ 1 3 Now again we'll be checking three
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is not divisible by
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four So it will come out And now you'll
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be checking So three is not equal to
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four So this else condition will be
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printed that four is not a perfect
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number You can see
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that So in this way this is the logic
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here mathematically defined what is a
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perfect number So in this way you can
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explain it It's very commonly asked
5:54
question in programming interviews and
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competitive exams And thank you very
5:59
much for watching this video and also
6:01
check out my website freemediatools.com
6:04
uh which contains thousands of tools
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