The first and root prime number is 2. This really comes from a reduced interpretation of the unconscious. Now in dynamic interaction the two poles (positive and negative) are fused and 0 (i.e. +1 - 1). However when separated both poles - from a conscious perspective - carry a positive sign. So in moving from 0 to 2 there is a fundamental confusion of conscious and unconscious. Put another way the unconscious (0) has a reduced (conscious) qualitative interpretation as 2 where both directions (external and internal) are given conscious expression. In this sense in contrast to the conscious approach which is one dimensional, the unconscious - in reduced linear terms - is two dimensional.
All (other) prime numbers which are odd are intimately linked to this root prime number 2. Mersenne primes represent one famous example of this approach. Thus 3 (which is prime) = 22 - 1.
Now psychologically, the prime structures relate directly to primitive (i.e. instinctive) understanding. The essence of such understanding is that the qualitative (dimensional) aspect of experience is directly confused with the quantitative. Alternatively the affective (personal) aspect is directly confused with the cognitive (impersonal). Indeed this always remains the basis of (blind) instinctive behaviour where personal desire is directly embodied in impersonal objects.
Thus psychological prime behaviour (where quantitative objects are confused with qualitative dimensions) directly complements mathematical prime numbers (where both are fully separated).
The next psychological stage involves a further transition whereby affective (personal) reality becomes gradually separated from (impersonal) matter. In other words there is the start of the recognition of a separate self and some extension of experience in space and time. However the directions of experience are still greatly confused. A clear sense of self is not yet possible.