Teaser 2445: [Divisible by 9]

From The Sunday Times, 2nd August 2009 [link]

I started with a list of six numbers (with no leading zeros, of course). Five of the six numbers were divisible by 9.

Then I coded the numbers by consistently using letters for digits, with different letters representing different digits.

In this way, the list became:

SETTER
SENT
PRETTY
EASY
SUNDAY
TEASER

Which of those words represented the number that was not divisible by 9?

This puzzle was originally published with no title.

[teaser2445]