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The smallest prime factor of the 43rd Lucas number. Note that the smallest prime factor of the next composite Lucas number with prime index can be obtained by deleting the first digit of 6709. The largest in the set of primes that appear in at least one of the nine basic solutions (not counting rotations of 120 degrees or reflections) to the Tetractys Puzzle: 2, 3, 5, 7, 13, 17, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 179, 239, 241, 251, 269, 271, 281, 283, 347, 359, 389, 479, 541, 569, 571, 593, 673, 709, 743, 821, 823, 853, 907, 953, 971, 983, 2389, 6709. (See puzzle.)
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