Am I an Automorphic Number?
Python 2, 24 bytes



lambda n:`n*1L`in`n**2L`


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For the first time in history, Python 2's appending an L to the repr of longs is a feature rather than a bug.

The idea is to check if say, 76^2=5776 ends in 76 by checking if 76L is a substring of 5776L. To make the L appear for non-huge numbers, we multiply by 1L or have 2L as the exponent, since an arithmetic operation with a long with produces a long.