Puzzle - solve it

This is a mathematical challenge, and it's been said that:
 
* If you're an engineer, you should be able to solve it in (within) 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 given below:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ans: 3263442

From: Shahid Habib Rana