85 is a number that preceeds 84 and proceeds 86. The prime factorization is 5*17. A number is divisible by 85 if it is divisible by 5 and 17. 85 is the largest n such that 1^2 + 2^2 + 3^2 + ... + n^2 = 1 + 2 + 3 + ... + m has a solution.

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