The square root of number 121 is "11". What is the square root of the number "12345678987654321."?

How many triangles can you count in the figure given?

When I asked a girl's name she told me her name is the date '07/09/2001'.

I thought for a few seconds and then I got her name. Do you?

Can you make four (4) nines (9) equal 100?

Write the next letter in this sequence.
O, T, T, F, F, S, S, E, __
**Hint: It is a Number Series Puzzle

Without looking at a calendar, within a minute name, a boy's name using 5 consecutive 1st letters of 5 consecutive months

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

Spot what is wrong here in below Picture?

What famous saying does this rebus mean?

COME SERVED <---
COME SERVED
COME SERVED
COME SERVED
COME SERVED

I have an eye but still cannot see.

Who am I?