Prime numbers

[Tugdual]

Regarding the original topic, I believe that considering digits is never a good idea. Digits are just the letters in a certain base that form words to represent a number. The number as a whole means something while the first digit (base 10) is the number modulo 10.
To go further, let's consider the prime numbers expressed in base 2. First digit would always be 1 otherwise it would be an even number, hence not prime. OMG 100% of the prime numbers start with a 1!! Shall we conclude anything? Obviously no, so studying the digits of a number seem pointless to me.
Always intersted to get your feedback.