Language: C

main(n,r,i){for(;scanf("%d",&n),r=-n,n;printf("%s",n>r?"deficien":n<r?"abundan":"perfec"),puts("t number"))for(i=1;i*i<=n;i++)n%i?0:r+=i+n/i,(i-n/i)?0:r-=i;}

Compiler output:
main.c:1:1: error: return type defaults to 'int' [-Wimplicit-int]
    1 | main(n,r,i){for(;scanf("%d",&n),r=-n,n;printf("%s",n>r?"deficien":n<r?"abundan":"perfec"),puts("t number"))for(i=1;i*i<=n;i++)n%i?0:r+=i+n/i,(i-n/i)?0:r-=i;}
      | ^~~~
main.c: In function 'main':
main.c:1:1: error: type of 'n' defaults to 'int' [-Wimplicit-int]
main.c:1:1: error: type of 'r' defaults to 'int' [-Wimplicit-int]
main.c:1:1: error: type of 'i' defaults to 'int' [-Wimplicit-int]
main.c:1:18: error: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
    1 | main(n,r,i){for(;scanf("%d",&n),r=-n,n;printf("%s",n>r?"deficien":n<r?"abundan":"perfec"),puts("t number"))for(i=1;i*i<=n;i++)n%i?0:r+=i+n/i,(i-n/i)?0:r-=i;}
      |                  ^~~~~
main.c:1:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
  +++ |+#include <stdio.h>
    1 | main(n,r,i){for(;scanf("%d",&n),r=-n,n;printf("%s",n>r?"deficien":n<r?"abundan":"perfec"),puts("t number"))for(i=1;i*i<=n;i++)n%i?0:r+=i+n/i,(i-n/i)?0:r-=i;}
main.c:1:18: warning: incompatible implicit declaration of built-in function 'scanf' [-Wbuiltin-declaration-mismatch]
    1 | main(n,r,i){for(;scanf("%d",&n),r=-n,n;printf("%s",n>r?"deficien":n<r?"abundan":"perfec"),puts("t number"))for(i=1;i*i<=n;i++)n%i?0:r+=i+n/i,(i-n/i)?0:r-=i;}
      |                  ^~~~~
main.c:1:18: note: include '<stdio.h>' or provide a declaration of 'scanf'
main.c:1:40: error: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
    1 | main(n,r,i){for(;scanf("%d",&n),r=-n,n;printf("%s",n>r?"deficien":n<r?"abundan":"perfec"),puts("t number"))for(i=1;i*i<=n;i++)n%i?0:r+=i+n/i,(i-n/i)?0:r-=i;}
      |                                        ^~~~~~
main.c:1:40: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:1:40: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
main.c:1:40: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:1:91: error: implicit declaration of function 'puts' [-Wimplicit-function-declaration]
    1 | main(n,r,i){for(;scanf("%d",&n),r=-n,n;printf("%s",n>r?"deficien":n<r?"abundan":"perfec"),puts("t number"))for(i=1;i*i<=n;i++)n%i?0:r+=i+n/i,(i-n/i)?0:r-=i;}
      |                                                                                           ^~~~
main.c:1:91: note: include '<stdio.h>' or provide a declaration of 'puts'
main.c:1:134: error: lvalue required as left operand of assignment
    1 | main(n,r,i){for(;scanf("%d",&n),r=-n,n;printf("%s",n>r?"deficien":n<r?"abundan":"perfec"),puts("t number"))for(i=1;i*i<=n;i++)n%i?0:r+=i+n/i,(i-n/i)?0:r-=i;}
      |                                                                                                                                      ^~
main.c:1:153: error: lvalue required as left operand of assignment
    1 | main(n,r,i){for(;scanf("%d",&n),r=-n,n;printf("%s",n>r?"deficien":n<r?"abundan":"perfec"),puts("t number"))for(i=1;i*i<=n;i++)n%i?0:r+=i+n/i,(i-n/i)?0:r-=i;}
      |                                                                                                                                                         ^~