just tested it against the 10000 first prime numbers in Sublime Text : 2462 prime numbers have a direct neighbour with the same last digit. That's nearly a quar

just tested it against the 10000 first prime numbers in Sublime Text : 2462 prime numbers have a direct neighbour with the same last digit. That's nearly a quarter of them... Edit: by taking into account sequences with 3 identical digits (110 occurrences), it's even more.