In Mathematics
84 is the sum of the first seven triangular numbers (making it a tetrahedral number), as well as the sum of a twin prime (41 + 43). Being thrice a perfect number, 84 is itself a semiperfect number.
84 is the lim sup of the largest finite subgroup of the mapping class group of a genus surface divided by .
A hepteract is a seven-dimensional hypercube with 84 penteract 5-faces.
Read more about this topic: 84 (number)
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“... though mathematics may teach a man how to build a bridge, it is what the Scotch Universities call the humanities, that teach him to be civil and sweet-tempered.”
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