The H. C. F. of 252,324 and 594 is

Find the prime factorization of each number: 252 = 2^2 × 3^2 × 7, 324 = 2^2 × 3^4, 594 = 2 × 3^3 × 11. The HCF is the product of the smallest powers of common prime factors: 2^1 and 3^2, giving 2 × 9 = 18.