11$\times$13=143

Let the side of square $1$ and square $2$ be $a$. Therefore square $3,4$ and $5$ have sides $a+1,a+2$ and $a+3$ respectively. Now, from diagram we can clearly observe that $(a+3)+(a+2)= (a+a)+(a+1)$. We get $a=4$. and area of the rectangle $=11\times13=143$.