With this UDF, you can convert a decimal number to any base (binary, oct, hex, base32, base64) and you can even create your own base.
#include <Array.au3>
$base64 = "A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z,a,b,c,d,e,f,g,h,i,"& _
"j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z,0,1,2,3,4,5,6,7,8,9,+,/"
$base32 = "A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z,2,3,4,5,6,7"
$base16 = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F"
$base8 = "0,1,2,3,4,5,6,7"
$base2 = "0,1"
$number = InputBox