The Dehn Invariant - Numberphile

The Brussels Choice - Numberphile

The Oldest Unsolved Problem in Math

Darts in Higher Dimensions (with 3blue1brown) - Numberphile

Zero Knowledge Proof (with Avi Wigderson) - Numberphile

Busy Beaver Turing Machines - Computerphile

The Math of Being a Greedy Pig - Numberphile

The Goat Problem - Numberphile

How Imaginary Numbers Were Invented

A New Discovery about Dodecahedrons - Numberphile

The hardest "What comes next?" (Euler's pentagonal formula)

Terrific Toothpick Patterns - Numberphile

How To Speak Fluently In English About Almost Anything

Epic Induction - Numberphile

Impossible Squares - Numberphile

The Simplest Math Problem No One Can Solve - Collatz Conjecture

The unexpectedly hard windmill question (2011 IMO, Q2)

The Strange Physics Principle That Shapes Reality

The Clever Way to Count Tanks - Numberphile

Riemann Hypothesis - Numberphile

The Riemann Hypothesis, Explained