Complex numbers adjoin i to the integers. Two dimensions. One relation: i² = -1. Magic numbers adjoin m = √i to the integers. Four dimensions. One relation: m⁴ = -1. Commutative, exact, integer. This paper defines the magic number ring M = Z[m], a four-dimensional commutative integer algebra generated by a single unit m satisfying m⁴ = -1, equivalently m = √i, the eighth root of unity (ζ₈). The ring is isomorphic to the classical cyclotomic integers Z[ζ₈], but is presented in a notation that foregrounds the defining property over the construction.\n\nThe paper develops: the closure relation and multiplication table; the silver ratio as a native algebraic element (δ = 1 + √2, with √2 = m + m⁻¹ the Hadamard scale); the real magic subring Z[√2] with the silver closure δ² = 2δ + 1; the complex tower Z ⊂ Z[i] ⊂ Z[m] with ranks 1, 2, 4; and matrix representations with all entries in {-1, 0, 1}.\n\nA central result is the primitive unit. The quadratic m² - √2·m + 1 = 0 gives 1 + m² = √2·m, but here the prime 2 splits the structure: the clean form 1 + m² = 1 + i is the ramified prime over 2 (norm 4, expanding by √2), not a unit. The primitive unit of norm 1 is M = m/δ = 1 - m + m², with modulus 1/δ, satisfying m = δ·M. This exactly mirrors the twist-number identity j = φ·J, with the silver ratio in place of the golden: both distinguished units contract by the inverse of their metallic ratio. Its matrix M_M has all entries in {-1, 0, 1}, determinant 1, and eigenvalues split by the silver ratio (moduli δ and 1/δ), the exact silver analogue of the twist kernel. The contrast with 1 + i is the whole point: 1 + i is the irreversible resource (the Hadamard scale, the bridge to measurement), while M = m/δ is the reversible kernel (the gate). In the twist numbers these two roles coincide in the single unit J = 1 + j²; the prime 2 splits them, and that split is the algebraic signature of quantum computation. The connection to quantum computation is exact. By the Kliuchnikov–Maslov–Mosca theorem, the ring Z[m, 1/√2] = Z[1/√2, i] is precisely the set of matrix entries of all single-qubit Clifford+T unitaries. The T gate is the magic unit m, the Hadamard is its real shadow √2, and the Clifford group lives in the Gaussian sub-ring. The grading is the Clifford hierarchy as a tower of square roots: the diagonal gate diag(1, ζ_{2^k}) sits at level k. Pauli Z = ζ₂ (level 1), Clifford S = ζ₄ = i (level 2), magic T = ζ₈ = m (level 3). The magic numbers Z[ζ₈] are precisely the third level of the Clifford hierarchy, the first level outside the Clifford group, hence the first that achieves universality: rank four as a module, level three in the hierarchy.\n\nThe magic numbers are the silver sibling of the twist numbers Z[ζ₅]. The two are quartic cyclotomic integer rings over the two smallest real metallic fields, disjoint over Q (since gcd(8,5) = 1), one carrying the forces (prime 5, gold) and one carrying the magic (prime 2, silver). Both metallic fundamental units have norm -1, and the top relations rhyme: j⁵ = 1 against m⁴ = -1. Companion to the twist numbers paper.