555

Do you mean one of these?

• The number 555 (math): I can factor it, convert bases, do modular arithmetic, etc. Quick facts: 555 = 3 × 5 × 37; in binary 1000101011; in hex 0x22B; digit sum 15.

• The 555 timer IC (electronics): I can explain operation modes (astable/monostable) and practice circuit problems.

• Something else (e.g., a code or topic your exam uses 555 for)?

Tell me which, and what level you’re studying. If you want, I can generate a quick 5-question set right away based on your choice.