3078

Number
$3078$ (three thousand and seventy-eight) is:


 * $2 \times 3^4 \times 19$


 * The $18$th pentagonal pyramidal number after $1, 6, 12, 40, 75, 126, 196, 288, 405, 550, 726, 936, 1183, 1470, 1800, 2176, 2601$:
 * $3078 = \displaystyle \sum_{k \mathop = 1}^{18} \dfrac {k \left({3 k - 1}\right)} 2 = \dfrac {18^2 \left({18 + 1}\right)} 2$