Palindrome
A sat whose number reads the same forwards and backwards in decimal, such as sat 1,221 or sat 12,321; sat 0 is not counted as one.
How a sat qualifies
Write the sat number in decimal, without separators. If the digits read the same reversed, the sat is a palindrome: 1,221, 12,321 and 1,111,111,111,111,111 are; 1,231 is not. Every single-digit sat from 1 to 9 is one too.
Sat 0 is the exception. A bare digit check would call "0" a palindrome, but the scanner the site's rules follow generates palindromes from sat 1, so sat 0 is never typed as one.
Counting every palindromic number from 1 up to the last sat, 2,099,999,997,689,999, gives 120,999,997 palindromic sats.
Kinds of palindrome
A palindrome is classified further by how many distinct digits it uses:
- 1D palindrome: one digit repeated, such as 1,111;
- 2D palindrome: exactly two, such as 1,221;
- 3D palindrome: exactly three, such as 12,321;
- four or more distinct digits: a palindrome with no further type.
Separately, a palindrome built from a shorter palindrome repeated, such as 121,121, is a perfect palinception. A block height can be a palindrome too; that is a different type, paliblock, about the block and not the sat number.
On this site
There is no plain Palindrome category. The site tracks the 1D and 2D palindromes and the perfect palinceptions everywhere, and any palindrome inside a historic range: block 9, 78, 286 and 666, the Nakamoto blocks, pizza, JPEG and Hitman, and the 3D palindromes of Silk Road. Those categories are listed below.