Factors of 81

The factors of 81 are 1, 3, 9, 27 and 81. That is 5 factors in total.

A factor of 81 is a whole number that divides 81 exactly, with no remainder. 81 is a composite number because it has factors other than 1 and itself.

Factor pairs of 81

Two numbers that multiply to give 81:

1 × 81 = 81
3 × 27 = 81
9 × 9 = 81

Prime factorization of 81

81 = 3 × 3 × 3 × 3 = 3⁴. The prime factors of 81 are 3.

Quick facts about 81

Is 81 prime? No.
Even or odd: odd.
Sum of its factors: 1 + 3 + 9 + 27 + 81 = 121.
81 is a perfect square (9 × 9), so it has an odd number of factors.

Factors of nearby numbers

Number	Factors
77	1, 7, 11, 77
78	1, 2, 3, 6, 13, 26, 39, 78
79	1, 79
80	1, 2, 4, 5, 8, 10, 16, 20, 40, 80
82	1, 2, 41, 82
83	1, 83
84	1, 2, 3, 4, 6, 7, 12, 14, 21, 28, 42, 84
85	1, 5, 17, 85

More about 81: 81 squared · square root of 81 · 81 in binary · 81 in Roman numerals.

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