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What is the remainder when 12! is divided by 13?

Competition practiceNumber & Arithmetic
  • A12
  • B0
  • C1
  • D11

Step-by-Step Solution

Wilson's theorem says that for a prime , the factorial ! leaves remainder on division by . Here , so 12! leaves 12. Checking directly, 12! = 479001600 and , a difference of 12. The trap is 0: a factorial is a multiple of everything up to itself, but 12! never picks up the factor 13, so it is not a multiple of 13.
Answer: A) 12

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