Stage: 3 Challenge Level: 
Possible extension.
This problem is a special case of Factorial Fun.
Possible support
See also Fac Finding and Factoring Factorials which are also special cases.
Workshop. Divisibility. smartphone. Working systematically. Modulus arithmetic. Prime factors. Multiplication & division. Properties of numbers. Factors and multiples. Factorials.
Published May 2002.
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