Is there an effecient approach to count the number of elements in a given range that can divide k?

count the number of elements in a given range that can divide k? Eg- in range 1 to 5 k=8 The no of elements that can divide k are 2,4. I want a logic which i can use in my cpp program. This is a simple example the value of k can extend till 10^5. Similar is the case of range.