In Ada, the number before #...# is the base of the number system, and the characters between #...# are the numbers in it.
Then the Irreducible_P variable is initialized in binary and is 141 decimal or 8d hexadecimal, which means Unicode Reverse Line Feed .
x and y initialized in hexadecimal notation. 16#53# is a character (byte) with the code 83 decimal or 'S' in ASCII , and 16#ca# is 202 decimal and the type of character depends on the encoding. For example, in cp1251 (windows) it is the Russian letter 'К' , in KOI8-R the letter 'й' , and in Latin-1 the letter 'й' 'Ê' .
(And, in fact, "if you look closely at a text in an unknown language, then gradually its meaning begins to reach you."
Checked in Google and here it is written in the Literals section).