When it's bad luck to meet a black cat?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

Can you find the company name in the pictogram below?

What 8 letter word can have a letter taken away and it still makes a word. Take another letter away and it still makes a word. Keep on doing that until you have one letter left. What is the word?

A little girl goes to the store and buys one dozen eggs. As she is going home, all but three break. How many eggs are left unbroken?

Which number comes next in the number series?

2, 9, 30, 93, ?

Two girls were born to the same mother, on the same day, at the same time, in the same month and year and yet they're not twins. How can this be ?

How many times do a clock's hands overlap in a day ?

I am a type of word that is spelt incorrectly or used differently, on purpose for humour. What am I?
Hint 1: You can find me in a joke.
Hint 2: I am a play on words.

10+10 and 11+11 can give you the same answer.

Explain how?