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Project Euler 23 Mystery Cache

Hidden : 1/18/2017
Difficulty:
3.5 out of 5
Terrain:
1.5 out of 5

Size: Size:   micro (micro)

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Geocache Description:

Acknowledgements


This cache was inspired by Project Euler.

General notes


  • To solve Project Euler puzzles, you will probably have to write a computer program.
  • Many of the containers are small, and contain neither pen nor pencil.
  • There are explicit finding notes in each geochecker.

Non abundant sums and products


A perfect number is a number for which the sum of its proper divisors is exactly equal to the number. For example, the sum of the proper divisors of 28 would be 1 + 2 + 4 + 7 + 14 = 28, which means that 28 is a perfect number.

A number n is called deficient if the sum of its proper divisors is less than n and it is called abundant if this sum exceeds n.

As 12 is the smallest abundant number, 1 + 2 + 3 + 4 + 6 = 16, the smallest number that can be written as the sum of two abundant numbers is 24. By mathematical analysis, it can be shown that all integers greater than 28123 can be written as the sum of two abundant numbers. However, this upper limit cannot be reduced any further by analysis even though it is known that the greatest number that cannot be expressed as the sum of two abundant numbers is less than this limit.

Find the product of all the positive integers which cannot be written as the sum of two abundant numbers, call this number P.


The Puzzle


P is a large number: it has 4,628 digits. The four digits starting at position 1,000 are [6,4,7,1]. To find this cache find the four digits starting at positions 4,219 and 3,955.

You can assume that the coordinates are N 52 1x.xxx E 0 x.xxx.


Additional Hints (Decrypt)

Frr gur trbpurpxre.

Decryption Key

A|B|C|D|E|F|G|H|I|J|K|L|M
-------------------------
N|O|P|Q|R|S|T|U|V|W|X|Y|Z

(letter above equals below, and vice versa)