155

Number
$155$ (one hundred and fifty-five) is:


 * $5 \times 31$


 * The $10$th second pentagonal number after $2, 7, 15, 26, 40, 57, 77, 100, 126$:
 * $155 = \dfrac {10 \left({3 \times 10 + 1}\right)} 2$


 * The $31$st positive integer $n$ such that no factorial of an integer can end with $n$ zeroes.