How many positive two-digit numbers less than 30 have an odd number of factors?
K kavitha New member Joined Dec 23, 2010 Messages 17 Jan 2, 2011 #1 How many positive two-digit numbers less than 30 have an odd number of factors?
tkhunny Moderator Staff member Joined Apr 12, 2005 Messages 11,339 Jan 2, 2011 #2 Define "factors". Do you mean "Proper divisors"? In any case, you may wish to ponder perfect squares. Write all the divisors of 24 and then write all the divisors of 25. Notice anything interesting?
Define "factors". Do you mean "Proper divisors"? In any case, you may wish to ponder perfect squares. Write all the divisors of 24 and then write all the divisors of 25. Notice anything interesting?
