Can you find out which number multiplied by itself will give the output as 12345678987654321?

I am white when I am dirty, and black when I am clean. What am I?

What seven-letter word has hundreds of letters in it?

If we tell you that there is a relation between the numbers and letters in the given figure, can you analyze it and find the missing letter in the last box?

I have thought of a number that is made up by using all the ten digits just once. Here are a few clues for you to guess my number:

First digits is divisible by 1.
First two digits are divisible by 2.
First three digits are divisible by 3.
First four digits are divisible by 4.
First five digits are divisible by 5.
First six digits are divisible by 6.
First seven digits are divisible by 7.
First eight digits are divisible by 8.
First nine digits are divisible by 9.
The number is divisible by 10.

Can you find out the number ?

I am the beginning of everything, the end of everywhere. I'm the beginning of eternity, the end of time and space. What am I?

Place the numbers from 1 to 9 in the circles in a manner that each side of the triangle sums up to 17.

Solve the alphametic puzzle by replacing the alphabet with the number.

S T O R M +
S O L E S
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T O W E L
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What number when divided in half becomes zero?

A network of 20 x 10 squares is given to you.

Can you calculate how many unique squares and rectangles can be formed combining two or more individual squares ?