Considering only positive integer factors, which of the following integers has an odd number of distinct factors?

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The positive factors for each number:

$$ 16: 1, 2, 4, 8, 16 $$ $$ 20: 1, 2, 4, 5, 10, 20 $$ $$ 23: 1, 23 $$ $$ 27: 1, 3, 9, 27 $$ $$ 35: 1, 5, 7, 35 $$