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.

Brachylog, 5 bytes

~√a₁?

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How it works

~√a₁?
~√      the input is the square root of a number
  a₁    whose suffix is
    ?   the input

Python 2, 31 bytes

Out-golfed by xnor... (this happens every single time) >< But hey, it's surprisingly Pythonic for code-golf.

People don't tend to remember Python has str.endswith()...

lambda n:str(n*n).endswith(`n`)

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