Can you solve the private eye riddle? - Henri Picciotto

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As Numberland’s best detective, you thought you’d seen it all. But the desiccated corpses of prominent natural numbers have been showing up all over the city. A lockdown is ordered from sundown to sunrise, and it’s still not enough to stop what can only be described as a vampiric feeding frenzy. Can you figure out why the citizens of Numberland are being attacked? Henri Picciotto shows how.


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Meet The Creators

  • Educator Henri Picciotto
  • Director Igor Coric, Artrake Studio
  • Narrator Addison Anderson
  • Music Greg Chudzik, Cem Misirlioglu
  • Sound Designer Cem Misirlioglu
  • Director of Production Gerta Xhelo
  • Editorial Director Alex Rosenthal
  • Producer Anna Bechtol
Additional Resources for you to Explore
Slime numbers are numbers that can be sliced into a sequence of primes.

For example, 41 (which is already prime), or 41075 → 41|07|5. Explore slime numbers in this worksheet (It is excerpted from the materials in Henri Picciotto’s Infinity, an elective high school math course).

When thinking about whole numbers, it is convenient to quickly recognize multiples of certain numbers. (For example, all multiples of 5 end in 0 or 5.) Wikipedia has a big list of divisibility tests.

Want more puzzles? TED-Ed has lots of fun and challenging brainteasers in our Riddle Series!

Customize this lesson

Create and share a new lesson based on this one.

About TED-Ed Animations

TED-Ed Animations feature the words and ideas of educators brought to life by professional animators. Are you an educator or animator interested in creating a TED-Ed Animation? Nominate yourself here »

Meet The Creators

  • Educator Henri Picciotto
  • Director Igor Coric, Artrake Studio
  • Narrator Addison Anderson
  • Music Greg Chudzik, Cem Misirlioglu
  • Sound Designer Cem Misirlioglu
  • Director of Production Gerta Xhelo
  • Editorial Director Alex Rosenthal
  • Producer Anna Bechtol

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