5062

This number is a composite.

506239841 {+0, +2, +6, +8} and 5062213991 {+0, +2, +6, +8} are prime. Note the first prime in each 4-tuplet share the first 4 digits (5062). If you add 4 to 506239841 and divide by 15 it equals 33749323, then 33749323 {-2, +0, +4, +6} along with 33749323 x 15 {-4, -2, +2, +4} are all prime. [Luhn]