Can you find the odd number in the following?

2716, 4135, 5321 and 7145

You see a boat filled with people, yet there isn’t a single person on board. How is that possible?

Replace the question mark with the correct number in the below-given picture?

A spaceship was lost. The detective was given a piece of paper. This was the location of the spaceship! This is what the slip had scribbled on it:
Juice, Umbrella, Potato, Ice, Tomato, Elephant, Rice.

Where is the spaceship?

There are people and strange monkeys on this island, and you can not tell who is who (Edit: until you understand what they said - see below). They speak either only the truth or only lies.
Who are the following two guys?
A: B is a lying monkey. I am human.
B: A is telling the truth.

Twenty frogs are sitting on a log floating on the surface of a river. Two of them decide to jump off into the water.

How many frogs are there on the log at this moment?

What number comes next in the series?

5 15 5 18 5 24 14 20 _

We have shown you a regular water barrel as below. Without using any measuring device can you check if the barrel is more than half-filled or less than half-filled?

Two friends were betting. One said to the other, "The coin will be flipped twenty times and each time the coin lands on the head, I will give you $2 and each time it lands on the tale, you will give me $3." After flipping the coin twenty times not a single penny was exchanged among them.

How many times did the coin land on heads?

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?