Can you fill the blank with the correct number?

6 30 870 756030 _____

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

A 3 digit number is such that it's unit digit is equal to the product of the other two digits which are prime. Also, the difference between it's reverse and itself is 396.

What is the sum of the three digits?

I am Huge on Sunday and Saturday.
I am small from Tuesday to Thursday.
I do not exist on Monday and Friday.
Who am I?

Can you find the mistake in the below statement?

Can you count the number of seconds in a year?

Clue: You need to bother about calculation.

I’m tall when I’m young, and I’m short when I’m old. What am I?

You stand in front of two doors. A guard stands next to each door. You know the following things: one path leads to paradise, the other leads to death. You cannot distinguish between the two doors. You also know that one of the two guards always tells the truth and the other always lies. You have permission to ask one guard one question to discover which door leads to paradise. What one question would you ask to guarantee you enter the door to paradise?

On the dull night when the blonde was dozing, she heard an odd clamour and she saw that there was a bizarre man with a gun simply outside her home. So she raced to the telephone to call the police, however, she can't dial 911. Why?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211