Prime numbers are used for secret writings (cryptography ...
If this seems a mere coincidence, then all doubts should be removed once we realize that joining these 7, 29, and 139 numbers lefttoright 729139 or righttoleft 139297 also produces in both cases primes with prime digit sums (7+2+9+1+3+9= 31) making them additive prime numbers too!Do you know how rare prime numbers are let alone additive prime numbers?