# Class Invariants

There are intrinsics [`HilbertClassPolynomial`](../../ModularArithmeticGeometry/ModularCurves/attribute-3.md#function-crvmod-hilb-cl-poly) and [`WeberClassPolynomial`](../../ModularArithmeticGeometry/ModularCurves/attribute-3.md#function-crvmod-weber-cl-poly) to compute the minimal polynomial over ${\mathbb{Q}}$ of the *j-invariant* associated to the imaginary quadratic order of discriminant $D$ or the smaller (in terms of coefficient size) minimal polynomial of an associated Weber function. These are described in detail in Section [Class Polynomials](../../ModularArithmeticGeometry/ModularCurves/attribute-3.md#crvmod-class-polys) of the Modular Curves chapter.