The factors of 21 are 1, 3, 7, and 21 ... four factors.
The factors of 23 are 1 and 23 ... two factors.
The factors of 25 are 1, 5, and 25 ... three factors.
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The factors of 12 are 1, 2, 3, 4, 6, and 12 ... six factors.
The factors of 18 are 1, 2, 3, 6, 9, and 18 ... six factors.
