Factor tree project...each student chose their own 2 or 3-digit number of which to find the prime factorization. The leaves represent the prime numbers. Then they worked with a partner to use prime factorization to find the GCF of both numbers. They were given 4 sentence frames from which to choose and then wrote their GCF between the trees.
Factor Tree! I made this when I was teaching prime factorization to 6th graders. The stars are prime numbers and the squares are composite numbers, which can be broken down again. The kids enjoyed making their own factor trees.