The greatest common factor (GCF) of 16 and 28 is 4. There are several methods to find the GCF of two numbers, including long division, Euclidean algorithm, and prime factorization. One way to find the GCF of 16 and 28 is to list their factors and find the greatest common factor. The factors of 16 are 1, 2, 4, 8, and 16, while the factors of 28 are 1, 2, 4, 7, 14, and 28. The largest number that divides both 16 and 28 without any remainder is 4, so the GCF of 16 and 28 is 4. Another way to find the GCF of 16 and 28 is to use the prime factorization method. The prime factorization of 16 is 2 x 2 x 2 x 2, and the prime factorization of 28 is 2 x 2 x 7. The common prime factors are 2 and 2, so the GCF of 16 and 28 is 2 x 2 = 4.