Numbers / 40

The Number 40

40 is composite: factorization 2^3 × 5. That gives 40 exactly 8 divisors: 1, 2, 4, 5, 8, 10, 20, 40. 40's proper divisors total 50, 10 more than 40 itself, so 40 is abundant. 40 has a digit sum of 4; for 40, the digital root works out to 4. 40: 2, 4, 5, 8, 10 all divide 40 evenly, out of 2-12. 40 is 101000 in binary and 28 in hex; as a Roman numeral it's XL.