New Scientist Enigma 509 – Banking on a Prime
by Paul de Sa
From Issue #1661, 22nd April 1989
I have two accounts at Midloids bank, both with unusual eight-digit account numbers, which are made up of a combination of all odd digits. If either of the account numbers is split in half it gives two four-digit prime numbers. These two primes contain the same four digits, but in a different order, and with no digit repeated. Furthermore if these four-digit primes are split in half, they each give two two-digit prime numbers. If, for both numbers, the prime formed from the first four digits is larger than the prime formed from the second four digits, what are the numbers of my accounts?