After S6 #The100finale there's a lot of questions about Becca (Erica Cerra ) and the world's organizations that gotta be answer on S7. Here's a thread.

Erica Cerra Jason Rothenberg The 100 The 100 Writers Room 1. Why is the global organization always divided into 13 factions?
The Ark was in 13 stations (before Polaris '13th station' was separate); On Earth there was 13 clans with skaikru, Second Dawn created 13 levels part and Sactum was ruled by 13 Primes.
How is that connected?