The "first philosopher" (not really). Influenced other thinkers who went on to create the major schools of philosophy. For example, he taught Plato some things, who then taught Aristotle.

And Antisthenes took to himself Socrates' character more than his ideas, and taught the famous Diogenes the Cynic, who taught Crates, who taught Zeno of Citium, who created Stoic philosophy.

The inventor of decimal numbers, sort of.

Developed al-jabr, i.e. algebra. Studied Indian numerals, and his works were translated into Latin in the 12th century, which introduced the West to decimal notation.