For clarity, I have reedited this question, by using some comments below, so I apologize if its contents is redundant with some comments...  

After works of Davis, Matijasevic, Putman and Robinson between 1960 and 1970, we know that every recursively enumerable set of numbers can be represented by a polynomial.   
In particular, it's the case for the set of prime numbers. 

In 1976, Jones-Sata-Wada-Wiens published (see [here][1]) the following polynomial $P$ of degree $25$ in $26$ variables $a$, $b$, $c$,..., $z$, admitting the property that $P(\mathbb{N})\cap \mathbb{N} = \mathbb{P}$, the set of prime numbers !   

$P(a,b,...,z) = (k+2)[1 – (wz+h+j–q)^{2} – [(gk+2g+k+1)(h+j) + h – z]^{2} -(2n+p+ $ 
$ q+z–e)^{2} – [16(k+1)^{3}(k+2)(n+1)^{2} + 1 – f^{2}]^{2}– [e^{3}(e+2)(a+1)^{2} + 1 –o^{2}]^{2} - [(a^{2}–1)y^{2} +  $ 
$ 1 –x^{2}]^{2}– [16r^{2}y^{4}(a^{2}–1) + 1 – u^{2}]^{2}– [((a+u^{2}(u^{2}–a))^{2}–1)(n+4dy)^{2} + 1 – (x+cu)^{2}]^{2} –[n+l+ $ 
$ v–y]^{2}– [(a^{2}–1)l^{2} + 1 – m^{2}]^{2} – [ai+k+1–l–i]^{2} –  [p + l(a–n–1) + b(2an+2a–n^{2}–2n–2) – m]^{2} – $ 
$ [q+ y(a–p–1) + s(2ap + 2a – p^{2} – 2p – 2)– x]^{2}– [z + pl(a–p) + t(2ap – p^{2} – 1) – pm]^{2}]$  


In "The Book of Prime Number Records" Paulo Ribenboim reports that: "It should be noted that this polynomial also takes on negative values, and that a prime number may appear repeatedly as a value of the polynomial."

I'm agree that this polynomial encodes an algorithm, but it's also a concrete polynomial, so it can be analyse by the tools of differential calculus to identify its extremal points and the area with positive range... I don't know if it's easy to compute, but now there exists very powerfull computers and supercomputers: $10^{6}$ times more powerfull than in 1989 when Paulo write its book...  

 So does anyone can explain to me if all this investigation I'm talking about would be useful to better understand the prime numbers ?



  [1]: http://mathdl.maa.org/images/upload_library/22/Ford/JonesSatoWadaWiens.pdf