mathematical challenge

‎​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) threeminutes (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 threemonths and if you're a lawyer, probably never. if you're good at math or logical problems, solve this challenge and theanswer is the password to open the spreadsheet to which you can add yourname to the hall of fame. What is the missing number in this logical series? 1, 2, 6, 42, 1806, ____???
Salam