The probability of a random shuffle resulting in starting order is 1 in 52!, or 1 in 8.06582*1067. If you did a perfect shuffle, in which last card was the first to come down, thus remaining last, it would only take 8 shuffles to be back to the starting order. If the 26th card was the first two come down then it would take 72 shuffles to back to the starting order.