C (gcc), 95(削除) 95 (削除ここまで) 94 bytes
Saved a byte thanks to ceilingcat !!!
a;b;c;d;r;f(n){for(b=0;n--;r=c>=b?b=c,n:r)for(c=0,d=n;d>9;++cd=n;a=d,d=d>9;++c)for(a=d,d=1;a;a;a;a/=10)d*=a%10;d=r;}
C (gcc), 95 bytes
a;b;c;d;r;f(n){for(b=0;n--;r=c>=b?b=c,n:r)for(c=0,d=n;d>9;++c)for(a=d,d=1;a;a/=10)d*=a%10;d=r;}
C (gcc), (削除) 95 (削除ここまで) 94 bytes
Saved a byte thanks to ceilingcat !!!
a;b;c;d;r;f(n){for(b=0;n--;r=c>=b?b=c,n:r)for(c=0,d=n;a=d,d=d>9;++c)for(;a;a/=10)d*=a%10;d=r;}