Numbers / 505

The Number 505

505 is composite: factorization 5 × 101. That gives 505 exactly 4 divisors: 1, 5, 101, 505. 505's proper divisors total just 107, 398 short of 505, the deficient case most of 505's neighbors share too. 505 is also a palindrome, since 505 reads identically forwards and backwards. 505 has a digit sum of 10; for 505, the digital root works out to 1. 505: 5 all divide 505 evenly, out of 2-12. 505 is 111111001 in binary and 1F9 in hex; as a Roman numeral it's DV.