4

1+2 = 4

2-1 = 4

3/2 = 4

4*0 = 4

1/4 = 4

1-3 = 4

2*2 = 4

2-4 = 4

3*1+1-2 = 4

1+2+3 = 4

1-2 =  4

4-1+0 = 4

3*2 = 4

1+1= 4

3-4 = 4

and the permutation and combination goes on and on

Confused ? This is what people have in their mind when you say just 4(and nothing more)

PS : 4 was just a random number chosen. No offence against other numbers ;)
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