How many positive integers have one less digit than their squares?

If we consider numbers of 1 or 2 digits the highest of these is 31, because 31^2 = 961 and 32^2 = 1024. So that gives us all integers between 4 and 31 inclusive. Total 28 integers.

No 3 digits number fits the bill so I think that is the answer

28 positive integers.