@abakcus Not impressed. There are too many prime numbers out there.

@abakcus Fascinating

@abakcus Now, I can say I know a 155-digit prime number. Thank you!

@abakcus What about 83 on down?

@abakcus How to prove it?

@abakcus @mathladyhazel 🤯

@abakcus Why is 43 cut in half? Now it looks like the difference between a 79 and 76 digits numbers

@abakcus If you keep adding digits to the left, following the same pattern, will you encounter an infinite number of primes? Or is this particular occurrence one of a finite handful, or is it unique?

@abakcus Yes, 821 is a prime number. 😏

@abakcus @mathladyhazel Add a zero on the end and it is no longer a prime number.

@abakcus @billsanti

@abakcus Yes, good.

@abakcus But it is unknown if there is a prime in this sequence. 1 12 123 1234 12345 123456 1234567 etc.

@abakcus It's beauty of mathematics

@abakcus How do you test that is it prime?

@abakcus @mathladyhazel Define f(n) to be "the concatenation of the digits from n to 1, written in descending order." Would be a fun student project to explore the primality properties of this sequence -- figuring out the algorithmic tests to use would be a large part of the fun! 🙂

@abakcus @mathladyhazel Related to A000422 in the OEIS

@abakcus How can we verify that this is true in a simple way?

@abakcus Prove it!

@abakcus My instinct is that primes of this form are rare...