555

Do you mean the number 555, or is that shorthand for a problem? If you’re just exploring the number, here are quick properties you can use in exams:

• Factorization: 555 = 3 × 5 × 37
• Number of divisors: (1+1)(1+1)(1+1) = 8
• Sum of divisors: (1+3)(1+5)(1+37) = 4 × 6 × 38 = 912
• Sum of proper divisors: 912 − 555 = 357
• Harshad (Niven) number: 555 is divisible by the sum of its digits (5+5+5 = 15); 555 ÷ 15 = 37
• Roman numeral: DLV
• Binary: 555 = 1000101011₂
• Base-3 representation: 555 = 202120₃

If you have a specific problem or subject (number theory, algebra, contest math), tell me and I’ll tailor a short solution or practice question.