10000...00001 (216-digits)

This number is a prime.

                                                                      100000
0000000000 0100000022 2222000000 0000222222 2222000000 0222000002 2220000000
0000002222 0000000000 0002222000 0000000000 2222000000 0000002222 0000000000
0022220000 0000000002 2222222222 2000000222 2222222220 0090000000 0000000001

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A prime that forms a "2" when placed in a 12-by-18 arrangement. See the Back Cover of "Prime Curios!: The Dictionary of Prime Number Trivia." [Loungrides]