This number is a prime.

                                                    72 2444466666 6888888889

+ The only prime formed by inserting in ascending order, between the digits of a double-digit number n, the concatenation of the even digits d, d times each of them, (n=79), i.e., zero 0’s, two 2’s, four 4’s six 6’s and eight 8’s. [Loungrides]

(There is one curio for this number that has not yet been approved by an editor.)

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