이문제 풀어보자

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,
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.

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. 

찬우씨는 보니까 풀더라 ㅋㅋ