Reference different sheets in excel formula

I am trying to reference different sheets in a quantity sum excel file. The sheets are listed by number, 1, 2, 3, etc. In the QSUM sheet, you reference cells from other sheets to fill in the quantity sum. For example, pulling a number from sheet 1 cell 25, ='1'!$C$25. I am currently just copying the equation over and over again, manually changing the sheet number within the cell. Is there a way to drag this equation down so that below it, it would read ='2'!$C$25, ='3'!$C$25, etc.?