Doctor, Engineer or Genius?

I got this through an e-mail from my friend in Australia :)

I was reading the start about how engineer takes 30 seconds to figure it out and a doctor in six hours, I got really, really fire up to solve it! The moment I look at it I knew the solution instantaneously. I'm not joking! :D

I took less than 30 seconds and i'm not an engineer! I'm a future doctor.

Either i'm good cause STPM train me or maybe I should consider a career in engineering! :) Or maybe i'm a genius?? Hahahaha

Too bad it requires me to download the new version of Microsoft Office or I would have enter my name in the wall of fame!

This is a mathematical challenge, and it's been said that:

If you're an engineer, you should be able to solve it in (under) three minutes (more like 30 seconds), if you're an architect, in three hours; if you're a doctor, in six hours; if you're an accountant, in three months and if you're a lawyer, probably never.
if you're good at math or logical problems, solve this challenge and the answer is the password to open the spreadsheet to which you can add your name to the hall of fame.
What is the missing number in this logical series?
1, 2, 6, 42, 1806, ____???
The answer is the password to open the spreadsheet that is attached to this email. If you figure it out, open the spreadsheet, type your name in, save it and resend it to your friends.
Good luck!