It is strange that some students start even number from 2 (i.e 2, 4, 6, 8, ...). Before start anything let us see the defination of even number.

"A number divisible by 2 is called even number"
2/2 = 1 (completely divisible by 2)
4/2 = 1 (completely divisible by 2)
6/2 = 1 (completely divisible by 2)
8/2 = 1 (completely divisible by 2)
Now 0 is also divisible by 2. i.e because 0/2 = 0
0
------
2 / 0
0
------
x
So zero is an even number because it is divisible by 2.
Even number should be start as 0, 2, 4, 6, 8, ...

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Even Number

A number divisible by 2 is called even number

According to defination of even number. Even number are 0, 2, 4, 6, 8, ...