193

193 is the number of compositions of 14 into distinct parts. In decimal, it is the seventeenth full repetend prime, or long prime. It is the only odd prime p {\displaystyle p} known for which 2 is not a primitive root of 4 p 2 + 1 {\displaystyle 4p^{2}+1}. It is the thirteenth Pierpont prime, which implies that a regular 193-gon can be constructed using a compass, straightedge, and angle trisector. It is part of the fourteenth pair of twin primes ( 191 , 193 ) {\displaystyle (191,193)}, the seventh trio of prime triplets ( 193 , 197 , 199 ) {\displaystyle (193,197,199)}, and the fourth set of prime quadruplets ( 191 , 193 , 197 , 199 ) {\displaystyle (191,193,197,199)}