I am sure there are many more or less difficult ways to imagine a world without the number 6. One way would be that operations giving 6 would be just undefined

I am sure there are many more or less difficult ways to imagine a world without the number 6. One way would be that operations giving 6 would be just undefined exactly like division by zero. The domain of the inverse function omits the number zero. Likewise, the x+1 function omits the number five in its codomain. And so on. However what happens if you look at decimal representations of numbers? Numbers like 16 aren't possible anymore, or are they? A save could be that we give it an own symbol like ∄. So we can write 16 as 1∄ instead. Because after all this exact point didn't disappear like zero didn't disappear just because it is undefined for the inverse function. But this feels like a very crappy cop-out. Let me stop here. I am sure this gets arbitrary the more one tries to move around in a world without the number 6.