# “Odd Positive Divisors”: Can the "trick" taught in the videos be used to find the number of odd positive divisors, including 1?

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• yang xu

Hello David, back to the odd divisor of 540 question.

you said 4 options on number 3 and 2 options on number 5

but it looks to me that the exponents of 3 and 5 cannot be both 0, right? if they are 0 the same time, 3^0 * 5^0 = 1, then 1 * 2^2, you will get an even divisor.

so it should be 7 odd divisors:  3, 3^2, 3^3, 3*5, 3^2*5, 3^3*5, 5

correct me if I am wrong. thanks!

• Erika K Fennelly

Can someone please answer the last comment? I'm also wondering if you're double or multiple-counting 1 as a divisor if you're counting 3^0 and 5^0...

• Siddhanth Ramani

Can someone let me know why this method work?

Thanks

• Ram Saamy

Why are you thinking as Chile, first you talk about prime factors then you take into account 3^0...etc...1 is not a prime factor so for 540=2x2x3x3x3x5. These are prime factors... You can not take as.. 540=2x2x3x3x3x5x1.. Leave 1 here... I think you got my point.. Thanks

• SURAJ GHOSH

Hi ,
2=2^1 ,4=2^2 ,8=2^3 etc
No. of factors =(1+1)=2
The rule for counting number of odd factors for N=2^n does not hold true

• Salma Shaik

Can u say me 18 odd and even factors and 600 also

• Salma Shaik

With solution