I did not come up with it, others did. सङ्गणक (saṅgaṇaka - IAST transliteration). It is composed of three parts - a prefix, root verb and a suffix -

सम् + गण् + ण्वुल् = सङ्गणक

sam + gaṇ + ṇvul = saṅgaṇaka

The prefix imparts the meaning of doing well. The verb means to calculate. The suffix converts the verb into a noun that performs that action. It literally means an entity that is adept at calculating.