Factors / Factors of 15

Factors of 15

1, 3, 5, 15

15 breaks into 2 pairs, tested up to √15 ≈ 3.9; each pair multiplies back to 15 exactly. 15's full pair list is (1, 15), (3, 5), for 4 divisors in total. 15's divisors other than 15 itself sum to just 9, 6 below 15: the common deficient case. 15 is odd, digit sum 6 for 15; small divisors of 15 include 3, 5. 15 has 4 divisors; 14 has 4 and 16 has 5, so 16 wins here. 15 divided by its largest divisor, 5, gives 3.