Why 1729 is a magic number? Answer Logically.

I come in different shapes and sizes.
Parts of me are curved, other parts are straight.
You can put me anywhere you like,
but there is only one right place for me.
What am I?

What is more useful when it is broken?

A girl rode into a tourist spot out of the city on Thursday. She loved the place and decided to stay for a few days. She stayed for four days and then she left for back home on Thursday.

How can this be possible?

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?

John is the son of Jacob.
So,
Jacob is the_____of John's father?

John is 45 years older than his son Jacob. If you find similarities between their ages, both of their ages contain prime numbers as the digits. Also, John's age is the reverse of Jacob's age.

Can you find their ages?

Can you complete the sequence puzzle?

AR TA GE CA LE VI LI _

What number when divided in half becomes zero?

Two guards were on duty outside a barracks. One faced up the road to watch for anyone approaching from the North. The other looked down the road to see if anyone approached from the South. Suddenly one of them said to the other, "Why are you smiling?"

How did he know his companion was smiling?