Can you replace the question mark with the correct number?

Can you count the number of squares in the figure below?

Find the next number in the series below

21 32 54 87 131 ?

Assume there are approximately 5,000,000,000 (5 billion) people on Earth. What would you estimate to be the result, if you multiply together the number of fingers on every person's left hand? (For the purposes of this exercise, thumbs count as fingers, for five fingers per hand.) If you cannot estimate the number then try to guess how long the number would be.

Sharpen your observation skills as you compare two seemingly identical images. Grab a magnifying glass, involve a buddy, and unleash your inner detective. Check the solution to see if you're a difference-detecting maestro!

Here is a conversation between a couple who both are software professionals.

Husband: Hey! What is your date of birth?
Wife Replied Angrily: It is 591062400
Husband after doing some calculations replied, "Got It".

What is the DOB of the wife?

Find the mistake in the below maths equations

A = 2
A(A-1) = 2(A-1)
A2-A = 2A-2
A2-2A = A-2
A(A-2) = A-2
A = 1

How many runs at maximum can a batsman score in a normal one-day match? Consider the fact that the conditions are ideal and there are no No Balls, no Wide Balls and no Extras in that match.

There are five vowels (a, e, i, o, u) in the English language.
Can you tell us a word that contains all these vowels?

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