87

Number
$87$ (eighty-seven) is:


 * $3 \times 29$


 * The $29$th semiprime:
 * $87 = 3 \times 29$


 * The $20$th lucky number:
 * $1, 3, 7, 9, 13, 15, 21, 25, 31, 33, 37, 43, 49, 51, 63, 67, 73, 75, 79, 87, \ldots$


 * The $2$nd positive integer after $1$ whose $\sigma$ value of its Euler $\phi$ value equals its $\sigma$ value:
 * $\sigma \left({\phi \left({87}\right)}\right) = \sigma \left({56}\right) = 120 = \sigma \left({87}\right)$

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