I think its because its 2 perfect numbers 496 and 28. As for the next one, thats an Australian one, Kevin 07 was his slogan, so 07 he came first, so 1 and there have been 25 PM's before him. So its 07125.
This is a project breakdown I did last year. Maybe some of it might be useful. Link to Zbrushcentral top row thread and breakdown http://www.zbrushcentral.com/showthread.php?200015-WXS-07-Depopulator Link to Allegorithmic interview on the project https://www.allegorithmic.com/blog/meet-danny-mcgrath-and-wxs-07-depopulator