86

Number

$86$ (eighty-six) is:

$2 \times 43$

The $7$th noncototient after $10$, $26$, $34$, $50$, $52$, $58$:

$\nexists m \in \Z_{>0}: m - \map \phi m = 86$

where $\phi \left({m}\right)$ denotes the Euler $\phi$ function

The $10$th nontotient after $14$, $26$, $34$, $38$, $50$, $62$, $68$, $74$, $76$:

$\nexists m \in \Z_{>0}: \map \phi m = 86$

where $\map \phi m$ denotes the Euler $\phi$ function

The $16$th happy number after $1$, $7$, $10$, $13$, $19$, $23$, $28$, $31$, $32$, $44$, $49$, $68$, $70$, $79$, $82$:

$86 \to 8^2 + 6^2 = 64 + 36 = 100 \to 1^2 + 0^2 + 0^2 = 1$

The $28$th semiprime:

$86 = 2 \times 43$

The $36$th integer $n$, and believed to be the largest, such that $2^n$ contains no zero in its decimal representation:

$2^{86} = 77 \, 371 \, 252 \, 455 \, 336 \, 267 \, 181 \, 195 \, 264$