6689

This number is a prime.

The smallest invertible prime whose digits are circular and composite. [Punches]

The NSW number with index 6689 is prime. These numbers arise when addressing the following question: "Is there a finite simple group whose order is a square?"

The first occurrence of a twin prime pair (6689, 6691) that both are invertible primes. [Beedassy]

The smallest invertible Yarborough prime. [Jha]

At midnight on the 8th of November 1942 a record-breaking attempt was made to assemble a "Liberty Ship", the SS ROBERT E. PEARY in less than five days. The ship was eventually completed in four days, fifteen hours and twenty-nine minutes = 6689 minutes. It was then launched into San Francisco bay.