39

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Number

$39$ (thirty-nine) is:

$3 \times 13$


The smallest positive integer having a multiplicative persistence of $3$.


The $15$th semiprime after $4$, $6$, $9$, $10$, $14$, $15$, $21$, $22$, $25$, $26$, $33$, $34$, $35$, $38$:
$39 = 3 \times 13$


The $21$st after $1$, $2$, $4$, $5$, $6$, $8$, $9$, $12$, $13$, $15$, $16$, $17$, $20$, $24$, $25$, $27$, $28$, $32$, $35$, $26$ of the $24$ positive integers which cannot be expressed as the sum of distinct non-pythagorean primes.


The $28$th integer $n$ such that $2^n$ contains no zero in its decimal representation:
$2^{39} = 549 \, 755 \, 813 \, 888$


The number of convex polygons that can be assembled from the complete set of $12$ hexiamonds.


Suggested by David Wells in his $1986$ book Curious and Interesting Numbers as being the smallest uninteresting number, which fact makes it intrinsically interesting.


Also see


Sources