The Prime Structure of Electromagnetic Constants

We systematically rewrite eighteen electromagnetic quantities in a canonical form built from the Riemann zeta value zeta(-3)=1/120 and the primes {2,3,5}. Starting from the zeta-Wyler identity alpha = 9*zeta(-3)^(1/4)/(16*pi^(11/4)), every quantity Q with mass dimension d decomposes as Q = m_e^d * f(2,3,5,pi,zeta(-3)), requiring only one experimental input (the electron mass) plus pure mathematics. Three structural results emerge: a Rationality Theorem (alpha^4*pi^11/zeta(-3) = 3^8/2^16), a Mirror Theorem linking quantum-vacuum alpha to thermal-vacuum zeta(4) via the functional equation, and an m_e-Separation Principle. All eighteen theoretical values match CODATA 2018 to within 0.30-3.05 ppm. Companion paper to 'The Arithmetic of Light' (doi:10.6084/m9.figshare.31744981).