Cannot parse `25RN`

[frenchy64]

user=> (fast-edn.core/read-string "25RN")
Execution error (NumberFormatException) at java.math.BigInteger/<init> (BigInteger.java:491).
Zero length BigInteger, offset: 4, context:
25RN
   ^

user=> (clojure.edn/read-string "25RN")
23

[frenchy64]

I have no idea what is happening here.

user=> 21RN
Syntax error reading source at (REPL:2:1).
For input string: "N" under radix 21

user=> 22RN
Syntax error reading source at (REPL:2:1).
For input string: "N" under radix 22

user=> 23RN
Syntax error reading source at (REPL:2:1).
For input string: "N" under radix 23

user=> 24RN
23
user=> 25RN
23
user=> 26RN
23
user=> 35RN
23
user=> 36RN
23
user=> 37RN
Syntax error reading source at (REPL:2:1).
Radix out of range

[tonsky]

N is a correct digit on radixes 24+