41,041

Number
$41 \, 041$ (forty-one thousand and forty-one) is:


 * $7 \times 11 \times 13 \times 41$


 * The $1$st Carmichael number with $4$ prime factors:
 * $41 \, 041 = 7 \times 11 \times 13 \times 41$


 * The $11$th Carmichael number after $561$, $1105$, $1729$, $2465$, $2821$, $6601$, $8911$, $10 \, 585$, $15 \, 841$, $29 \, 341$:
 * $\forall a \in \Z: a \perp 41 \, 041: a^{41 \, 040} \equiv 1 \pmod {41 \, 041}$


 * The $286$th triangular number:
 * $41 \, 041 = \ds \sum_{k \mathop = 1}^{286} k = \dfrac {286 \times \paren {286 + 1} } 2$

Also see

 * Carmichael Number with 4 Prime Factors