Product of all primes less than 20

[Canon80]

If you wanted to find out the product of all primes less than 20, which is closest to 10^x

2-3-5-7-11-13-15-17. Is there a shortcut to this or is it just a problem that you need to multiply out?

The answer is that it's closest to 10^7



Thank You

[reiserchen]

I cant help u with that but 15 is not a prime instead 19.

[kevin]

If you wanted to find out the product of all primes less than 20, which is closest to 10^x

2-3-5-7-11-13-15-17. Is there a shortcut to this or is it just a problem that you need to multiply out?

The answer is that it's closest to 10^7



Thank You

If you are good with your multiplication tables, you could cut this question down to size by thinking:

(2 x 3 x 17) x (5 x 19) x (7 x 13 ) x 11

approx 10^2 x 10^2 x 10^2 x 10

[GMATguru]

where did you find this problem?