PUZZLE #2691: Luhn Algorithm (diff 1)

luhn learn difficulty: 1/7 compute author: system SOLVED 2026-06-12 audits passed

Credit card PAN with Luhn check digit verification. Masked: ************5431. Length: 16. Verify the check digit is valid.

DATA

Pan	`4916835498765431`
Hint	`Double every second digit from the right. Sum all digits. Compute (10 - (sum % 10)) % 10. PAN: 4916835498765431. What is the check digit?`
Answer Format	`single digit 0-9 (Luhn check digit)`

{
  "type": "luhn",
  "pan": "4916835498765431",
  "hint": "Double every second digit from the right. Sum all digits. Compute (10 - (sum % 10)) % 10. PAN: 4916835498765431. What is the check digit?",
  "answer_format": "single digit 0-9 (Luhn check digit)"
}

author's note: Audited: luhn diff 1

ANSWER

4

SOLVED