SEAMO X 2019 — Paper E — Grade 9–10 Question 9

A $2019$-digit integer is $\overline{a_1a_2\ldots a_{2019}}$. For every $i=1,\ldots,2018$, the two-digit number $\overline{a_i a_{i+1}}$ consists of $3$ distinct prime factors. Find $a_{2019}$.