Posted by **Joe** on Tuesday, May 10, 2011 at 4:35pm.

If M=(1*2*3*4*......*1000) + 1, is M prime? I said no because 24001 can only be divided by 1 and itself, but I got a point off. Why is this?

- Math -
**Reiny**, Tuesday, May 10, 2011 at 6:00pm
probably since

1*2*3*4*...*1000 ≠ 24001

(just multiplying the last 3 numbers, 1000*999*998 is already 997002000, and we still have to multiply that by 997 other numbers.)

on the other hand, M is prime.

(I tried to figure out how you got 24000, and just realized that you simply multiplied 1*2*3*4*1000.

Did you not know what the .... in between the numbers meant ???)

- Math -
**Frank**, Tuesday, May 10, 2011 at 6:24pm
Oh i did 1 times 2 times 3 times 4=24, then times the 1000 which is equal to 24000, then on the outside of thefraction it says add 1 so that's how i got 24,001. I don't know what the ...means that's how the problem was written. How does that make it prime though if you don't know the actual number?

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