Answer
$15,548,000$
Work Step by Step
There are 10 different digits and 26 letters.
The first to letters can be any of the 26 letters.
The last letter can only be one of 23 letters (Because it can not be I,O or Q)
The three digits can be one of 10 digits.
This gives a total of $26*26*23*10*10*10=15,548,000$