I have been trying to compute the least cost to reach 1800 urban centres (destinations) from 432 different villages (origins) using the DEM file as cost information.
I would appreciate it if anyone suggests me an elegant way to compute the least cost to reach the destinations.
Are you trying to calculate the optimal path from villages to urban centres using a road network? If so, Network Analyst is the right tool for that job. However, you need a road network, not a DEM. Here is a tutorial to get you started: https://pro.arcgis.com/en/pro-app/latest/help/analysis/networks/od-cost-matrix-tutorial.htm
But since you mentioned a DEM, does that mean you actually want the least-cost path through the DEM, like a watershed analysis? If so, this is not the correct forum. You should ask your question in the Spatial Analyst forum: https://community.esri.com/t5/arcgis-spatial-analyst-questions/bd-p/arcgis-spatial-analyst-questions