1661

This number is a composite.

+ The smallest invertible palindromic semiprime. [Capelle]

+ prime(1*6*6*1)*π(1*6*6*1) = 1661. It is the largest known (up to 10^7) with this property. [Firoozbakht]

Printed from the PrimePages <primes.utm.edu> © G. L. Honaker and Chris K. Caldwell