2. $975 \times 935 \times 972 \times(\quad)$, to make the last four digits of this product all "0", what is the smallest number that should be filled in the parentheses?

To make the last four digits of this product all "0", what is the smallest number that should be filled in the parentheses?
2. The answer should be 20
2.【Solution】To make $975 \times 935 \times 972 \times$ () end with four "0"s, the product should be able to factor out 4 "5"s and 4 "2"s. $975=5 \times 5 \times 39, 935=5 \times 187, 972=2 \times 2 \times 243$, the first three numbers together have 3 "5"s and 2 "2"s, so the number to be filled in the blank is: $2 \times 2 \times 5=20$.