Prime time
Number Theory
Level
2
What is the largest seven-digit number that contains each of the digits 1 through 7 and has the property that the sum of any two consecutive digits is a prime number?
The answer is 7652341.
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
Taking 7 we see that then the preceeding / proceeding digits with which sum is a prime number are 6,4
With 6 are 7,5,1
With 5 are 2,6
With 4 are 1,3,7
With 3 are 2,4
With 2 are 1,3,5
With 1 are 2,4,6
So our largest number starts with 7 then we have 6,4 we choose 6 as it is greater than 4
So 7 after this 6 then 5 then 2 then 3 then 4 then 1 So we finally get 7652341 Upvote if u like this