Brachylog, 1 byte

ḟ

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###Explanation

ḟ is a built-in that asserts the following relation: its output is the factorial of its input. We simply give it a set output and see whether it suceeds or not with a variable input.

Brachylog, 1 byte

ḟ

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Explanation

ḟ is a built-in that asserts the following relation: its output is the factorial of its input. We simply give it a set output and see whether it suceeds or not with a variable input.

Brachylog, 2 bytes

~ḟ

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Technically this could be only 1 byte, if you put the Input in the first argument .

###Explanation

ḟ is a built-in that asserts the following relation: its output is the factorial of its input. We simply give it a set output and see whether it suceeds or not with a variable input.

Brachylog, 1 byte

ḟ

Try it online!

###Explanation

ḟ is a built-in that asserts the following relation: its output is the factorial of its input. We simply give it a set output and see whether it suceeds or not with a variable input.