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'Weekly Problem 35 - 2011' printed from http://nrich.maths.org/

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Find the number:
 

it's less than $100$;
it's one more than a multiple of $3$;
exactly one of its digits, you get a prime;
if you reverse its digits, you get a prime;
it has exactly four factors;
the sum of its digits is prime;
if you multiply it by $5$, the answer is greater than $100$.
 
 
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas. 

 

 

This problem is taken from the UKMT Mathematical Challenges.

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