189
This number is a composite.
The product of the four primes in a prime quadruplet (except for 5,7,11,13) always ends in 189. [Rupinski]
The 189th century would be the first to contain as few as five prime years (18803, 18839, 18859, 18869 and 18899).
(There are 2 curios for this number that have not yet been approved by an editor.)
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