One issue that needs to be clarified here is the relationship as between number and other mathematical symbols. On the one hand it would be valid to maintain that the fundamental nature of reality (as phenomenally revealed) is mathematical. However I would also contend that it is more precisely related to number.
Basically I would maintain that number in fact implicitly requires other key mathematical symbols and relationships.
For example I have frequently identified 1 with the (straight) line and 0 with the circle. So there are intimate links here as between key numerical and geometrical notions.
Also the important operations of addition and subtraction are again implied by the most basic of numbers (1 and 0). The very recognition of form in any context implies 1. So for example if one distinctly recognises an object this implies the corresponding inherent recognition of 1. So without such recognition one would not be even able to differentiate objects in experience.
However equally implied by such recognition is the (conscious) positing of the object (which is the holistic meaning of +).
The awareness of emptiness - which in holistic terms is 0 - by contrast requires the ability to (unconsciously) negate recognition of distinct objects. So quite literally in both analytical and holistic terms 1 - 1 = 0.
Without this ability to dynamically negate - to a degree - distinct phenomena in experience, integration would not be possible.
So what we have here established is that from a holistic mathematical perspective, 1 and 0 are intimately related to both differentiation and integration respectively. And these two processes are fundamental with respect to all phenomena (in both physical and psychological terms).
The derivation of further numbers then arises from these basics.
If instead of the complementary relationship 1 - 1 we consider 1 + 1, we then generate 2 (as a new number) which in holistic terms defines all duality in experience. This also serves as the first prime number. Now we can generate all the natural numbers through considering 2 + 1, 3 + 1, etc.
However equally these natural numbers will serve as unique expressions of the product of prime numbers. So in this relationship as between prime numbers and natural numbers (and natural numbers and prime) the operations of multiplication and division are born.
Ultimately I would maintain that all the key mathematical operations, symbols relationships etc. are implied through the recognition of numbers (when considered in both analytic and holistic terms).
More correctly perhaps it should be said that they imply each other. So it is not strictly the case that the numbers come first in recognition but rather that they both simultanously arise (in implicit fashion).
So in this sense to say that all reality - at the phenomenal level - is number, is really a more emphatic way of maintaining that such reality is mathematical.
In a previous contribution I mentioned that the qualitative nature of phenomena arises through differing configurations of space and time (to which these are related).
Now once again these configurations are related directly to number (when interpreted in a holistic sense).
In this context 1 can be identified with linear type reason that serves as the basic for scientific understanding as conventionally understood (and by extension standard conceptions of space and time).
0 by contrast would be identified with pure intuition at the other extreme from reason. This would be especially relevant to a contemplative type vision of reality. Unfortunately it is not incorporated in current notions of science which therefore possess a strong - merely - quantitative bias.
However all other numbers (apart from 0 and 1) are associated with intermediate type interpretation where both reason and intuition are formally included. So when such numbers are holistically used as dimensions we generate an unending range of new configurations (real and imaginary) through which space and time are configured.
Once again, as I have repeatedly explained in these contributions, the appropriate holistic structure associated with a number (as dimension) is intimately related to its corresponding root form.
The two roots of 1 are + 1 and - 1. In corresponding complementary fashion 2 as holistic dimension combines both positive and negative polarities of form in a dynamically interactive manner (where linear and circular notions of understanding are involved). Applied to space and time this likewise implies that too must be conceived at this level of understanding in terms of complementary opposite polarities.
Ever more intricate configurations with both real and imaginary aspects are then associated with dimensions > 2.
The qualitative nature of phenomena then arises from the varied mixing of such dimensions giving unlimited complexity with respect to possible space and time configurations.
So we can see in this manner that the true nature of space and time has a profound holistic mathematical rationale (as befits its inherent qualitative nature).
Thus object phenomena that are initially conceived in a quantitative manner continually interact with space and time dimensions (that are qualitative in nature). So the uniqueness of the various phenomena we experience, coincides with the corresponding (holistic) uniqueness of the dimensions with which they interact.