We know the relationship between HCF and LCM for two numbers \( a \) and \( b \) is given by:
\[
\text{HCF}(a, b) \times \text{LCM}(a, b) = a \times b.
\]
Given that:
- \( \text{HCF}(255, 867) = 51 \),
- \( a = 255 \),
- \( b = 867 \).
Substitute the values into the formula:
\[
51 \times \text{LCM}(255, 867) = 255 \times 867.
\]
Calculate \( 255 \times 867 \):
\[
255 \times 867 = 221085.
\]
Now, solve for LCM:
\[
\text{LCM}(255, 867) = \frac{221085}{51} = 4335.
\]
Conclusion:
The value of \( \text{LCM}(255, 867) \) is \( 4335 \).