555

Here are quick math notes about 555, plus a tiny practice set you can use for exams.

Facts about 555

• Decimal: 555
• Prime factorization: 3 × 5 × 37
• Divisors: 1, 3, 5, 15, 37, 111, 185, 555
• Number of divisors: 8
• Sum of divisors: 912
• Binary: 1000101011
• Hex: 0x22B
• Palindrome: yes (reads the same forward and backward)
• Divisibility: divisible by 3, 5, and 15

Mini practice

1. Compute gcd(555, 666).
2. Find 555 mod 7, and determine the modular inverse of 555 modulo 7.
3. If n = 555x is divisible by 100, what must x be a multiple of?

If you want, I can tailor a short practice set to a specific topic (factorization, modular arithmetic, divisibility rules, etc.).