Sage Math - Sage is a free open-source mathematics software system licensed under the GPL.
PARI/GP - PARI/GP is a widely used computer algebra system designed for fast computations in number theory - factorizations, algebraic number theory, elliptic curves, modular forms, L functions..
Autodesk Fusion 360 - Integrated CAD, CAM, and CAE featuring collaborative editing and cloud-based computation.
Mathcad - Mathcad is engineering calculation software that drives innovation and offers significant process...
Maxima - Maxima is a fairly complete computer algebra system written in Lisp with an emphasis on symbolic computation.
SMath Studio - Tiny, powerful, free mathematical program with WYSIWYG editor and complete units of measurements support.