In Mathematics
86 is the 25th distinct semiprime and the 13th of the form (2.q). The aliquot sum of 86 is 46 within the aliquot sequence (86,46,26,16,15,9,4,3,1,0) 86 being the 17th composite number in the 3-aliquot tree.
86 is the middle number in the second cluster of three discrete semiprimes between 85 and 87 being themselves discrete semiprimes.
86 is a semiprime, nontotient, a noncototient, a happy number, and a self number. It appears in the Padovan sequence, preceded by the terms 37, 49, 65 (it is the sum of the first two of these).
Since it is possible to find sequences of 86 consecutive integers such that each inner member member shares a factor with either the first or the last member, 86 is an Erdős–Woods number.
86 is a repdigit in base 6 (222).
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