Mathematically speaking, and putting aside other variables, a 6-digit PIN has one hundred times the number of possible combinations than a 4-digit PIN does.

Video There's nothing particularly difficult about cracking a smartphone's four-digit PIN code. All it takes is a pair of thumbs and enough persistence to try all 10,000 combinations. But hackers ...

Apple to require 6-digit passcodes on newer iPhones, iPads under iOS 9 Stronger passcode ups the ante: there will be one million possible permutations.