Answer
5!, called 5$\times$4$\times$3$\times$2$\times$1, is the product of all positive integers from 5 down through 1, by definition, 0! = 1.
Work Step by Step
5!, called 5$\times$4$\times$3$\times$2$\times$1, is the product of all positive integers from 5 down through 1, by definition, 0! = 1.