61

This number is a prime.

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

The first of five consecutive primes that can be arranged in a 3-by-3 square whose columns and rows sum to consecutive primes (199, 211, 223):

   61  67  71 

   67  71  73 

   71  73  79.

The smallest prime of order n that divides the sum of the first n composite numbers. [Silva]