Question

Prove that
3999991 is not prime

Answer 1

@noided @tcarroll010

Answer 2

@.Sam.

Answer 3

Hit: add 9 to this number

Answer 4

that's gonnabe easy, just prove that there is a number apart from itself and 1 that can divide it

Answer 5

*Hint

Answer 6

ok

Answer 7

can you notice anything special about the resulting number?

Answer 8

no, please help

Answer 9

what number do you get if you add 9 to your number?

Answer 10

1997
2003

Answer 11

?

Answer 12

you can divide the number by these two numbers

Answer 13

and you'd get an integer value

Answer 14

which means it is not a prime

Answer 15

QED

Answer 16

is the goal of this site to actually give constructive info?

Answer 17

3999991 + 9 = 4000000 = 4 * 10^6

the resulting number is a perfect square - agreed?

Answer 18

ok

Answer 19

because if so, I'm sorry

Answer 20

ok

Answer 21

I am fully agreed Now.

Thank you Sir

Answer 22

so then you have:

3999991 + 9 = 4 * 10^6

therefore:

3999991 = 4 * 10^6 - 9

the right-hand-side is a difference of two squares. this can always be factored. therefore 3999991 cannot be prime.

Answer 23

ah that's what you were doing
interesting.
thanks!

Answer 24

yw :)

Answer 25

Ok Thanks

Answer 26

yw :)