66,066

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Number

$66 \, 066$ (sixty-six thousand and sixty-six) is:

$2 \times 3 \times 7 \times 11^2 \times 13$

The $7$th palindromic triangular number after $0$, $1$, $3$, $6$, $66$, $3003$ whose index is itself palindromic:

$66 \, 066 = T_{363}$

The $14$th palindromic triangular number after $0$, $1$, $3$, $6$, $55$, $66$, $171$, $595$, $666$, $3003$, $5995$, $8778$, $15 \, 051$

The $363$rd triangular number:

$66 \, 066 = \ds \sum_{k \mathop = 1}^{363} k = \dfrac {363 \times \paren {363 + 1} } 2$

Also see

• Previous  ... Next: Palindromic Triangular Numbers with Palindromic Index
• Previous  ... Next: Palindromic Triangular Numbers
• Previous  ... Next: Triangular Number

Sources

• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $363,474,363$