How many factors does 6! have?

How many distinct positive integer factors does 6 ! 6! have?

Notation: ! ! is the factorial notation. For example, 8 ! = 1 × 2 × 3 × × 8 8! = 1\times2\times3\times\cdots\times8 .


The answer is 30.

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1 solution

There are two ways to solve this problem:


1 ) 1) 6 ! = 6 5 4 3 2 1 6!=6*5*4*3*2*1 , and we have to prime factorize this.

This means that it is for 6 6 , 3 2 3*2 .

For 5 5 , 5 5 .

For 4 4 , 2 2 2*2 .

For 3 3 , 3 3 .

And for 2 2 , 2 2 .

So the prime factorization of 6 ! 6! is 3 2 5 2 2 3 2 3*2*5*2*2*3*2 , and this is 2 4 3 2 5 1 2^4*3^2*5^1 .

And if we add 1 to each of the exponents, in this case 4, 2, and 1, we get 5, 3, and 2.

If we multiply all of these numbers, 5 3 2 5*3*2 , we get 30 \boxed{30} .


2 ) 2) We could calculate 6 ! 6! and get that it is 720 720 , and do the same process as we did above.

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