Improve multiplication, division and factoring skills. Think FACTOR! Don't just multiply and divide. That's what players must do while having fun playing rummy-like card games with this unique deck of 171 cards. Rules booklet defines four different card games, six deck levels, and includes math rules and strategies. The durable, standard-sized cards are attractively packaged in a sturdy box with storage tray. Players form factor sets. Because 20 = 4 x 5, the numbers 20, 4, and 5 form a factor set. Factor sets can have more than 3 cards. For example, the numbers 60, 4, 3 and 5 form a factor set because 60 = 4 x 3 x 5. Prime wild cards are used for prime numbers only. Adapts to many levels. Ages 7 years to adult.