69

Number
$69$ (sixty-nine) is:
 * $3 \times 23$


 * The $24$th semiprime:
 * $69 = 3 \times 23$


 * The $20$th Ulam number after $1$, $2$, $3$, $4$, $6$, $8$, $11$, $13$, $16$, $18$, $26$, $28$, $36$, $38$, $47$, $48$, $53$, $57$, $62$:
 * $69 = 16 + 53$


 * The $4$th after $21$, $29$, $61$ of the $5$ $2$-digit positive integers which can occur as a $5$-fold repetition at the end of a square number


 * The only integer whose square and cube use each of the digits from $0$ to $9$ exactly once each:
 * $69^2 = 4761$, $69^3 = 328 \, 509$

Also see

 * Number whose Square and Cube use all Digits Once