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Problem #55

Double Devils

All numbers of the form 6_6_6_0_0_6_6_6_0_0, where each _ can be any single digit, are called double devil numbers (for example, 6160630507696864040 is a double devil number).

Let x be the unique number whose square is a double devil number. Find x.

Contributed by Jay Hitesh Bosamiya

Solved by 223 users

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