We write the product 
<math xmlns="http://www.w3.org/1998/Math/MathML">
<mrow><mn>5</mn><mo>&#x00D7;</mo><mn>4</mn><mo>&#x00D7;</mo><mn>3</mn><mo>&#x00D7;</mo><mn>2</mn><mo>&#x00D7;</mo><mn>1</mn></mrow></math> as 5! and call this factorial 

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five. 

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Similarly 
<math xmlns="http://www.w3.org/1998/Math/MathML">
<mrow><mi>n</mi><mo>!</mo><mo>=</mo><mi>n</mi><mo stretchy="false">(</mo><mi>n</mi><mo>-</mo><mn>1</mn><mo stretchy="false">)</mo><mo stretchy="false">(</mo><mi>n</mi><mo>-</mo><mn>2</mn><mo stretchy="false">)</mo><mo>&#x2026;</mo><mn>2</mn><mo>&#x00D7;</mo><mn>1</mn></mrow></math>. Investigate the number of divisors of n!.

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