2007

2007 is divisible by 9. If a 1 be added onto the end... 20071, the number is prime. What can be added to the end of 20071, to obtain another prime?

What delights can be found beyond?

Brute force numerical calculation tells me to keep adding 3s. Is there a trick to see it without a computer?

Originally posted by DeepThought
Brute force numerical calculation tells me to keep adding 3s. Is there a trick to see it without a computer?

Originally posted by Mathurine
probably... 😉