191

This number is a prime.

Single Curio View: (Seek other curios for this number)

191 is the sum of 19th and 1st triangular number. It is the smallest and only known prime with this property, as of 21 August 2025. [Gupta]

Submitted: 2025-08-21 11:48:45; Last Modified: 2025-10-01 00:43:24.