Calculate the number 2540

Once there was a little boy that lived in the country. They had to use an outhouse, and the little boy hated it because it was hot in the summer and cold in the winter and stank all the time.The outhouse was sitting on the bank of a creek and the boy determined that one day he would push that outhouse into the creek. One day after a spring rain, the creek was swollen so the little boy decided today was the day to push the outhouse into the creek. So he got a large stick and started pushing. Finally,the outhouse toppled into the creek and floated away. That night his dad told him they were going to the woodshed after supper.Knowing that meant a spanking, the little boy asked why.
The dad replied, "Someone pushed the outhouse into the creek today.It was you, wasn't it son?"
The boy answered yes. Then he thought a moment and said, "Dad, I read in school today that George Washington chopped down a cherry tree and didn't get into trouble because he told the truth."
The dad replied, "Well, son, George Washington's father wasn't in the cherry tree."