The mathematical function factorial is defined as the product of a positive integer and all lesser positive integers. It is symbolized by the exclamation mark. For example

• 1! = 1
• 2! = 2 × 1 = 2
• 3! = 3 × 2 × 1 = 6
• 4! = 4 × 3 × 2 × 1 = 24
• 5! = 5 × 4 × 3 × 2 × 1 = 120
• 6! = 6 × 5 × 4 × 3 × 2 × 1 = 720
• 7! = 7 × 6! = 5,040
• 8! = 8 × 7! = 40,320
• 9! = 9 × 8! = 362,880
• 10! = 3,628,800
• 11! = 39,916,800
• 12! = 479,001,600