Question 15
There is a row of coins, numbered from 1 to 2006, each with head facing up. In the first round, coins whose numbers are divisible by 1 are turned over. In the second round, coins whose numbers are divisible by 2 are turned over. In the third round, coins whose numbers are divisible by 3 are turned over, and so on. In the 2006th round, coins whose numbers are divisible by 2006 are turned over. How many coins will have heads facing up after the 2006th round?