A unique prime number is a number that has no other prime numbers that can be divided into it. Prime numbers are whole numbers (like 1, 2, 3, 4, 5, etc.) that can't be divided by anything except 1 and themselves. A unique prime number is like a special prime number that only happens once and can't be divided by any other prime number. For example, the number 11 is a unique prime because it can't be divided by any other prime number.