I don't think it exists because you can always copyright some piece of self-created digital art so that it hashes to the number (if the hash maps to enough bits to represent that number).

I think there is a biggest number though, and it should be higher than 64bit-1 because your processor would otherwise occasionally handle illegal numbers, thereby (probably) making it illegal as well.

My point is rather than if we agree that large-enough numbers can be data, then there is a number at which they start to be data, N say, then "all numbers greater than or equal to N are data" uses N not as data, but as "counting and measuring". So this distinction is self-contradictory, so incoherent.

You could just say "greater than N-1" to avoid this problem, so this doesn't seem like a very strong argument.

I think the better point to make is that the law will never actually produce a concrete N, preferring to leave itself vague so that it can criminalise things at a whim. This is what makes it a farce and why such notions need to be purged from the law.

How can you subtract 1 from data?

You don't. That was subtraction on a meta level. You name the largest non-data number instead of naming the smallest data "number".

the fact that you cannot identify the exact number of sand grains that make a collection into a heap of sand does not mean heaps of sand do not exist

At least in the case of sand you can give examples of numbers of grains that don't constitute a heap, and numbers that do. And numbers smaller than the former will be non-heaps and numbers larger than the latter will be heaps.

For natural numbers, the lawyers seem unable to do even that. Sure, they might want to name some of the "illegal primes" mentioned in this thread as examples, but what will they say about those numbers +1? They're gonna paint themselves into a corner of ridiculousness nomatter what.

N = 10^85

You’ll know it when you see it.