Four-Digit Prime Numbers by Tens (Part 2: 2000-3000)
You will be given four four-digit numbers that differ only by the last digit being 1, 3, 7, or 9. Answer which ones are prime numbers. Example: If you are given "21, 23, 27, 29", only 23 and 29 are prime numbers, so you should choose "3, 9"