Xenocrates was born in approximately 396 BCE in Chalcedon (in present day Turkey). He was a student of Plato, joining the Academy in approximately 376 BCE, and eventually becoming head of the Academy in approximately 340 BCE. Xenocrates' main work apparently consisted of codifying Plato's philosophy.
Xenocrates agreed with Pythagoras on the importance of numbers. He is thought to have written two books, neither of which survive: On Numbers, and The Theory of Numbers. Xenocrates was an early proponent of the atomic theory, believing that all matter is composed of indivisible units.
To students of probability, Xenocrates is important because of his formulation of one of the first combinatorial problems: computing the number of syllables that could be constructed from the letters of the alphabet. According to Plutarch, Xenocrates solution was \(1\,002\,000\,000\,000\).