The missing number is 601.
The numbers in the sequence are all prime numbers, except for the missing number. The missing number must be a prime number that is greater than 598 and less than 611. The only prime number that satisfies these conditions is 601.
A prime number is a natural number greater than 1 that is not a product of two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number.