555

Do you mean the number 555 in a math context, or something else (e.g., 555 timer IC, Roman numerals DLV)? Here are quick math facts you can use for exams:

• Prime factorization: 555 = 3 × 5 × 37
• Divisors: 1, 3, 5, 15, 37, 111, 185, 555 (8 divisors)
• Sum of divisors: 912
• Digit-sum test: 5+5+5 = 15, so divisible by 3 (but not by 9)
• Divisibility:
  • Divisible by 3, 5, 15, 37, 111, 185, 555
  • Not divisible by 9 or 11
• Roman numeral: 555 = DLV
• Binary representation: 555 = 1000101011 (2^9 + 2^5 + 2^3 + 2^1 + 2^0)

If you’d like, I can turn this into a quick practice problem (e.g., find gcd(555, n), or list all divisors, or prove the factorization). Which topic would you prefer?