| 21st Century (Radio Edit) | 3:34 | |
| 21st Century (Original Full Length Mix) | 7:09 | |
| 21st Century (Transfer Club Mix) | 7:35 | |
| 21st Century (Francois K Remix) | 8:57 | |
| 21st Century (Different Gear Mix) | 8:46 |
| Title, Format | Label | Cat# | Country | Year | |
|---|---|---|---|---|---|
| 21st Century (CD, Maxi) | Addiction Records | ADICT116CD | Australia | 2001 | |
| 21st Century (12") | Multiply Records | TMULTY78 | UK | 2001 | |
| 21st Century (12", Promo) | Multiply Records | 12MULTY 78PY | UK | 2001 | |
| 21st Century (12", Promo) | Multiply Records | 12MULTY 78P | UK | 2001 | |
| 21st Century (12", Promo) | Multiply Records | 12MULTY 78PX | UK | 2001 | |
| 21st Century (12", Promo) | Multiply Records | PRO3817 | UK | 2001 | |
| 21st Century (CD, Maxi, CD1) | Multiply Records | CDMULTY 78 | UK | 2001 | |
| 21st Century (CD, Single, CD2) | Multiply Records | CXMULTY78 | UK | 2001 | |
| 21st Century (CD, Maxi) | Multiply Records | TWR0007-2 | UK | 2002 |
referencing 21st Century, 12", Promo, 12MULTY 78PY