Why 1729 is a magic number? Answer Logically.

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.

The first two letters signify a male, the first three letters signify a female, the first four letters signify a great, while the entire world signifies a great woman. What is the word?

Always in you, Sometimes on you;

If I surround you, I can kill you.

What am I?

How many letters are in the alphabet?

Which is the correct shadow of the bird?

I have a clock(12-hour format) and both the needles of the clock overlap at 12:00.
After how much time, they will overlap again?

This is a most unusual paragraph. How quickly can you find out what is so unusual about it? It looks so ordinary, you'd think nothing was wrong with it. Actually, nothing IS wrong with it. But it is not as ordinary as you might think. If you think about it for a bit, you will find out why it is truly so unusual. So what is it? What is so unordinary about this paragraph?

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see?

If an electric train is travelling south, then which way is the smoke going?