Here's a more revealing test:
unsigned int i;
for (i = 0; i < 60; i++) { unsigned long long l = 45ULL << i; printf("%llu - ", l); print_size(l, "\n"); }
prints:
45 - 45 Bytes 90 - 90 Bytes 180 - 180 Bytes 360 - 360 Bytes 720 - 720 Bytes 1440 - 1.9 KiB 2880 - 3.3 KiB 5760 - 6.1 KiB 11520 - 11.7 KiB 23040 - 23 KiB 46080 - 45 KiB 92160 - 90 KiB 184320 - 180 KiB 368640 - 360 KiB 737280 - 720 KiB 1474560 - 1.9 MiB 2949120 - 3.3 MiB 5898240 - 6.1 MiB 11796480 - 11.7 MiB 23592960 - 23 MiB 47185920 - 45 MiB 94371840 - 90 MiB 188743680 - 180 MiB 377487360 - 360 MiB 754974720 - 720 MiB 1509949440 - 1.9 GiB 3019898880 - 3.3 GiB 6039797760 - 6.1 GiB 12079595520 - 11.7 GiB 24159191040 - 23 GiB 48318382080 - 45 GiB 96636764160 - 90 GiB 193273528320 - 180 GiB 386547056640 - 360 GiB 773094113280 - 720 GiB 1546188226560 - 1.4 TiB 3092376453120 - 2.8 TiB 6184752906240 - 5.6 TiB 12369505812480 - 11.2 TiB 24739011624960 - 22.5 TiB 49478023249920 - 45 TiB 98956046499840 - 90 TiB 197912092999680 - 180 TiB 395824185999360 - 360 TiB 791648371998720 - 720 TiB 1583296743997440 - 1.4 PiB 3166593487994880 - 2.8 PiB 6333186975989760 - 5.6 PiB 12666373951979520 - 11.2 PiB 25332747903959040 - 22.5 PiB 50665495807918080 - 45 PiB 101330991615836160 - 90 PiB 202661983231672320 - 180 PiB 405323966463344640 - 360 PiB 810647932926689280 - 720 PiB 1621295865853378560 - 1.4 EiB 3242591731706757120 - 2.8 EiB 6485183463413514240 - 5.6 EiB 12970366926827028480 - 11.2 EiB 7493989779944505344 - 6.5 EiB
That last one is probably an overflow.