What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

Can you replace the question mark with the correct number in the below table sequence?

What is a word made up of 4 letters, yet is also made up of 3. Sometimes is written with 9 letters, and then with 4. Rarely consists of 6, and never is written with 5.

These types of puzzles are known as charades. What you have to do is to find two words that are referred to in the first stanza and the second stanza and put them together to form the third word in the third stanza.

Just for example, if my first refers to 'off' and my second refers to 'ice', then my whole will be the 'office'.

My first is present - future's past -
A time in which your lot is cast.

My second is my first of space
Defining people's present place.

My whole describes a lack of site -
A place without length, breadth, or height.

Two batsman each on 94 runs. Seven runs needed to win in last 3 balls. Both make 100*. How?

Make eight squares by moving only two matchsticks.
Note- Square can be of different sizes.

What has 13 hearts but no other organs?

Can you name four days which start with the letter 'T'?

John is asked to stand behind Jacob and Jacob is asked to stand behind John. Both of them feel confused about it and don't know what to do?

But it is quite possible, do you know how?

Next Number in the Series,

5, 16, 49, 104, ?