Are there any "perfect" squares?

Number Theory Level 1

A positive integer is called "perfect" if it's equal to the sum of its proper divisors. For example, 6 is a perfect number because the proper divisors of 6 are 1,2 and 3 and 6=1+2+3. 28 is another example of a perfect number because 28=1+2+4+7+14.

Are there any perfect numbers which are also perfect squares?