Step 1: Use the relation between HCF, LCM and product.
For two positive integers \(a\) and \(b\):
\[
a \times b = \text{HCF}(a,b) \times \text{LCM}(a,b).
\] Step 2: Substitute the given values and solve for LCM.
\[
8670 = 17 \times \text{LCM} \;\Rightarrow\; \text{LCM} = \frac{8670}{17} = 510.
\] Step 3: Conclude.
Hence, the LCM is \(510\).