Factors / Factors of 399

Factors of 399

1, 3, 7, 19, 21, 57, 133, 399

399 breaks into 4 pairs, tested up to √399 ≈ 20.0; each pair multiplies back to 399 exactly. 399's full pair list is (1, 399), (3, 133), (7, 57), (19, 21), for 8 divisors in total. 399's divisors other than 399 itself sum to just 241, 158 below 399: the common deficient case. 399 is odd, digit sum 21 for 399; small divisors of 399 include 3, 7. 399 has 8 divisors; 398 has 4 and 400 has 15, so 400 wins here. 399 divided by its largest divisor, 133, gives 3.