Find The Next Number in this series.
1, 2, 6, 42, 1806 ?

Why do we preferably have round manhole covers and not square ones?

An American nightclub called 'The Coconut Grove' had a terrible fire in which over 400 people died. A simple design flaw in the building led to a high death toll. Subsequently, regulations were changed to ensure that all public buildings throughout the country eliminated this one detail, which proved deadly. What was it?

Which word is least like the others? Third, fourth, fifth, sixth, seventh, eighth, ninth?

Mr. Buttons was all set to go to the village of Buttonland to meet his friend. So, he packed his bags and left for the village at 5 in the morning. Upon travelling on a road for miles, he came across a point where the road diverged into two. He was confused on which road to take. He gazed around and he saw two owls sitting on a branch. He thought he could ask for directions for the village from the two owls. So he went to the tree. There he saw a sign which read, "One owl always lies, and one is always truthful. They both fly away if you ask them more than 1 question."
Mr. Buttons was caught in the dilemma of what to ask? And from which owl to ask, since he only had one question. What should Mr. Buttons ask?

What is at the end of a rainbow?

If a wheel has 54 spokes, how many spaces are there between the spokes?

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

What is black when you buy it, red when you use it, and gray when you throw it away?

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?