555

Do you mean:

• 555 as Thai internet slang for laughter, or
• a math problem set involving the number 555?

If you want math practice, here’s a compact mini-set you can use right away:

• Prime factorization: 555 = 3 × 5 × 37
• Divisors: 1, 3, 5, 15, 37, 111, 185, 555 (8 divisors)
• Sum of divisors σ(555) = (3+1)(5+1)(37+1) = 4×6×38 = 912
• Sum of proper divisors = 912 − 555 = 357 (deficient since 357 < 555)
• Euler’s totient: φ(555) = φ(3)φ(5)φ(37) = 2×4×36 = 288
• Quick problems:
  1. gcd(555, 1000) = 5
  2. How many multiples of 555 are ≤ 9999? 18 (since floor(9999/555) = 18)
  3. Is 555 prime? No (it’s 3×5×37)

If you also want a Roman numeral version: 555 = DLV.

Tell me which you prefer and I’ll tailor more problems or explanations.