That would be:

...61893587

We start writing the digits right to left an pi/4 is about 0.78539816...

So you found a flaw in Cantor's diagonal argument?

https://en.wikipedia.org/wiki/Cantor%27s_diagonal_argument

They are just saying “but what if we replace the set of integers with a larger set”. I think they are also defining this larger set in a base 10 specific way.

I think they basically mean the 10-adic numbers, which, unlike the p-adics for p a prime number, uh, I forget exactly what goes wrong, but I suspect it has like, zero divisors or something like that.