The Highest Common Factor (HCF) is the largest number that divides two numbers exactly. To find the HCF of 420 and 130, we can use the Euclidean algorithm.

Step 1: Divide 420 by 130. The remainder is 30.
Step 2: Now, divide 130 by the remainder 30. The new remainder is 10.
Step 3: Divide 30 by the remainder 10. The remainder is 0.
Therefore, the HCF is the last non-zero remainder, which is 10.

Final Answer: 10