555

Do you mean 555 as a math problem (the number), or something else like the 555 timer IC in electronics? If you’re prepping for exams, here are quick math facts about the number 555, in case that’s what you want:

• Prime factorization: 555 = 3 × 5 × 37
• Divisors: 1, 3, 5, 15, 37, 111, 185, 555
• Number of divisors: 8
• Sum of all divisors: 912; sum of proper divisors: 912 − 555 = 357
• 555 is a deficient number (sum of proper divisors < the number)

A couple quick practice problems (with answers):

• gcd(555, 270) = 15
• lcm(555, 28) = 15,540
• 555 mod 13 = 9

If you meant the 555 timer IC, I can give a quick overview of its modes (monostable, astable, bistable) and pinout. Which one would you like?