108 (number)

108 (one hundred [and] eight) is the natural number following 107 and preceding 109. Its prime factorization is $3 \times 2 \times 3 \times 3 \times 2$

108 is:

• an abundant number.
• a semiperfect number.
• a tetranacci number.
• the hyperfactorial of 3 since it is of the form .
• divisible by the value of its φ function, which is 36.
• divisible by the total number of its divisors (12), hence it is a refactorable number.
• the angle in degrees of the interior angles of a regular pentagon in Euclidean space.
• palindromic in bases 11 (99₁₁), 17 (66₁₇), 26 (44₂₆), 35 (33₃₅) and 53 (22₅₃)
• a Harshad number in bases 2, 3, 4, 6, 7, 9, 10, 11, 12, 13 and 16
• a self number.
• an Achilles number because it is a powerful number but not a perfect power.
• nine dozen

There are 108 free polyominoes of order 7.

The equation $2 \sin\left ( \frac{108^\circ}{2} \right ) = \phi$ results in the golden ratio.

This could be restated as saying that the "chord" of 108 degrees is , the golden ratio.