Numbers / 403

The Number 403

403 is composite: factorization 13 × 31. That gives 403 exactly 4 divisors: 1, 13, 31, 403. 403's proper divisors total just 45, 358 short of 403, the deficient case most of 403's neighbors share too. 403 has a digit sum of 7; for 403, the digital root works out to 7. 403 shares no factor with 2-12; 403's own divisors start beyond that range. 403 is 110010011 in binary and 193 in hex; as a Roman numeral it's CDIII.