Quick Tips:

• Divisible by 2 → last digit is even
• Divisible by 3 → sum of digits is divisible by 3
• Divisible by 5 → last digit is 0 or 5
• Divisible by 9 → sum of digits is divisible by 9
• Divisible by 10 → last digit is 0
• Divisible by 11 → alternating sum of digits is divisible by 11. E.g., 2728 (2-7+2-8 = -11)