19

This number is a prime.

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

The sequence of smallest odd prime numbers with exactly n circular loops begins 19, 83, 89, 809, 1889, 8089, ... . Circular loops occur in the digits 0, 6, 8, or 9 only. Note that the digit 8 contains two loops. [Mutter]