其它
How many $0$s are there in the end of the result of the factorial of $25$? 
Overseas Competition->Knowledge Point->Calculation Modules->Operations through Formulas->Factorization
We can get $1+1+1+1+2=6$ factor $5$s from $5, 10, 15, 20, 25$ in total, which can make six $10$s after multiplying $2$. Six $10$s means that there should be $6$ $0$s in the end. 