What lock combination did Feynman find by using digits of e?

Feynman found the lock combination 27-18-28 by using the opening digits of the mathematical constant e, 2.71828.

While working at Los Alamos during the Manhattan Project, Feynman became interested in the combination locks protecting filing cabinets and desks. He discovered that some locks had mechanical tolerances and that colleagues often chose predictable settings. For one cabinet, he guessed that a physicist might use a notable mathematical number rather than a random sequence.

The sequence 27-18-28 corresponds to the digits of e after the decimal point is written as a three-part combination: 2.71828. His guess opened a cabinet containing sensitive research notes, and he found that several cabinets used the same combination. Feynman then left notes behind as a prank, alarming colleague Frederic de Hoffmann.

This episode is often described as Feynman “cracking the atomic-bomb safes,” but the story involved filing cabinets and exploitable habits, not breaking a modern high-security vault. The anecdote illustrates both his mechanical curiosity and his fondness for playful demonstrations of human carelessness.