21603 is the Postal Code/ZIP Code for the District of Santa Isabel in the Costa Rica Province of Alajuela and the Canton of Río Cuarto.
| Postal Code | 21603 |
| Postal Code Name | Santa Isabel |
| Province | Alajuela Province |
| Canton | Río Cuarto Canton |
| Timezone | Central Standard Time (CST) |
| Adjacent Postal Codes | 21006 21602 41002 41005 |