Can you solve this amazing hard number series problem?
7, 8, 10, 12, 16, 18 ?

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

What is the riddle which can be asked all day with a different correct answer each time.

A high school has a strange principal. On the first day, he has his students perform an odd opening day ceremony:

There are one thousand lockers and one thousand students in the school. The principal asks the first student to go to every locker and open it. Then he has the second student go to every second locker and close it. The third goes to every third locker and, if it is closed, he opens it, and if it is open, he closes it. The fourth student does this to every fourth locker, and so on. After the process is completed with the thousandth student, how many lockers are open?

I have a hole in my back and legs I lack.
I live where I can’t breathe and I eat without teeth.
What am I?

An artist while painting a scenic beauty, decides to paint three layers of blue colour on the sky.

Which layer will go on the first?

How can you make number one disappear by adding something to it?

Two fathers and two sons decided to go to a shop and buy some sweets upon reaching. Each of them bought 1 kg of sweet. All of them returned home after some time and found out that they had 3kg of sweets with them.

They did not eat the sweets in the way, nor threw or lose anything. Then, how can this be possible?

I start and end with 500 and carry a 5 in my heart. But I require the first letter and the first number to be complete. I am the name of a King.

Who am I ?

Our product and our sum always give the same answer. Who are we?