Heronian tetrahedron
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A Heronian tetrahedron is a tetrahedron whose sides, faces and volume are all rational numbers. The faces must therefore all be Heronian triangles. A regular tetrahedron with rational sides is not a Heronian tetrahedron because its face areas and volume are not rational numbers. A Heronian tetrahedron is sometimes called a perfect tetrahedron. 117 is the smallest possible length of the longest side of a perfect tetradhedron.