19 26 67 | September 21, 2017, the day the world learned about Mad Dog Mattis' other nickname, 'Chaos'

https://www.armytimes.com/news/your-marine-corps/2017/09/21/mattis-explains-the-origin-of-the-call-sign-chaos/
The nicknames 'Mad Dog' and 'Chaos' have gematria of 26 each, going with the fact that Mad Dog became the 26th Secretary of Defense.

Notice the headlines above were from September 21, 2017, discussing his nickname 'Chaos'.

9/21/2017 = 9+21+20+17 = 67 (67, the 19th prime number)