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#7 Home primes
Set by Peter Rowlett
To find the home prime of a number, follow this procedure: first, find its prime factors; then concatenate these by writing the prime factors in size order to form a new number using all of their digits; then repeat until the resulting number is prime.
For example, 9 = 3 × 3, so its prime factors are 3 and 3. These concatenate to give 33. Now, find the prime…
