Fixnums in KCL are those integers in the range -(2 to the power of 31) to (2 to the power of 31)-1, inclusive. Other integers are bignums. Thus 25 factorial (25!)
15511210043330985984000000
is certainly a bignum in KCL.
Common Lisp constants related to integers have the following values in KCL.
most-positive-fixnum = 2147483647 = (2 to the power of 31)-1 most-negative-fixnum = -2147483648 = - (2 to the power of 31) boole-1 = 3 boole-2 = 5 boole-and = 1 boole-andc1 = 4 boole-andc2 = 2 boole-c1 = 12 boole-c2 = 10 boole-clr = 0 boole-eqv = 9 boole-ior = 7 boole-nand = 14 boole-nor = 8 boole-orc1 = 13 boole-orc2 = 11 boole-set = 15 boole-xor = 6
See Chapter 12 of the Common Lisp Reference Manual for their meanings.