Teaser 2919: Letters puzzle

From The Sunday Times, 2nd September 2018 [link]

My best friend has a special birthday later this month, and I have composed a Teaser to celebrate the occasion.

First of all, I wrote that date as a single number (with the day at the start, the month in the middle and the year at the end).

Then, replacing different letters consistently with different non-zero digits, I found that the sum of LETTERS and PUZZLE gives that number.

Send in your prime value for TEASER.