4095

Number
$4095$ (four thousand and ninety-five) is:
 * $3^2 \times 5 \times 7 \times 13$


 * The $5$th and last Ramanujan-Nagell number after $0$, $1$, $3$, $15$:
 * $4095 = 2^{12} - 1 = \dfrac {90 \times \paren {90 + 1} } 2$


 * The $6$th odd abundant number after $945$, $1575$, $2205$, $2835$, $3465$:
 * $\map {\sigma_1} {4095} - 4095 = 4641 > 4095$


 * The $90$th triangular number after $1$, $3$, $6$, $10$, $15$, $\ldots$, $3655$, $3741$, $3828$, $3916$, $4005$:
 * $4095 = \ds \sum_{k \mathop = 1}^{90} k = \dfrac {90 \times \paren {90 + 1} } 2$