The smallest prime number is 2, and the smallest composite number is 4. To find the Highest Common Factor (HCF) of these two numbers, we need to identify their factors.
The factors of 2 are: 1, 2
The factors of 4 are: 1, 2, 4
The common factors of 2 and 4 are: 1, 2. Among these, the highest is 2.
Therefore, the HCF of the smallest prime number (2) and the smallest composite number (4) is 2.