Missing digits in 19!

Number Theory Level 1

$\large 19! = \overline{12164510{\color{#3D99F6}a}4{\color{#3D99F6}a}8832000}$

Determine the digit ${\color{#3D99F6}a}$ .

Note: $19 ! = 19 \times 18 \times 17 \times \cdots \times 2 \times 1$