11

This number is a prime.

Just showing those entries submitted by 'Missailidis': (Click here to show all)

Take all twin primes (including the "Siamese twins" 2,3) less than 11, namely: (2,3), (3,5), (5,7). If we square each prime and then add the squared prime pairs together, we get 121. Or, 11^2. [Missailidis]