Primes again!

Let S S be a set of prime numbers such that every digit from 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 1,2,3,4,5,6,7,8,9 appear only once in the set.

Let T T the sum of those primes in S S . What is the smallest possible T T ?

As an explicit example, we could have S = { 5 , 7 , 293 , 4861 } S=\{5,7,293,4861\} so T = 5166 T=5166 .


The answer is 207.

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1 solution

Abdeslem Smahi
Aug 11, 2015

To obtain the smallest possible T T we must try to use only one or two digits primes.

if we have a two digits prime so the digits ( 2 , 4 , 5 , 6 , 8 ) (2,4,5,6,8) must appear in the 1 0 s . 10's. but the 2 2 and 5 5 could appear as a single digit prime So :

the smallest T T should be T = 1 + 2 + 3 + 5 + 7 + 9 + 40 + 60 + 80 = 207. T=1+2+3+5+7+9+40+60+80=207.

and the possible sets S S are:

{ 2 , 3 , 5 , 41 , 67 , 89 } , { 2 , 3 , 5 , 47 , 61 , 89 } , { 2 , 5 , 7 , 43 , 61 , 89 } \boldsymbol \{2, 3, 5, 41, 67, 89\}, \boldsymbol \{2, 3, 5, 47, 61, 89\}, \boldsymbol \{2, 5, 7, 43, 61, 89\}

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