To find the Highest Common Factor (HCF) of 25 and 27, we can use the prime factorization method or the Euclidean algorithm.

1. Prime factorization:
   • 25 = $5^2$
   • 27 = $3^3$

There are no common factors between 25 and 27 other than 1. Therefore, the HCF is 1.

Would you like further details or have any questions?

Here are 5 related questions you might want to explore:

1. What is the LCM of 25 and 27?
2. How is the Euclidean algorithm used to find the HCF of two numbers?
3. Can you explain the difference between HCF and LCM?
4. What is the prime factorization of 100?
5. How do you find the HCF of three numbers?

Tip: The HCF of two numbers is always a divisor of their difference.