[CentOS] Size of /var/log/lastlog

Hi,

Can any of you explain this weirdness:

[root at machine log]# cd /var/log/
[root at machine log]# ls -la|grep last
-r--------   1 root  root  1254130450140 Nov  6 21:44 lastlog
[root at machine log]# du -hs lastlog
52K     lastlog

What's up with the output of ls? This is x86_64.

Thanks,

Morten