As far as I know, HWSD (Harmonized World Soil Database) might be handy in this case. Find it here: http://www.fao.org/land-water/land/land-governance/land-resources-planning-toolbox/category/details/en/c/1028012/ or here https://www.2w2e.com/home/GlobalSoilHwsd
Additionally, you may find the global FAO/UNESCO soil database (in a SWAT-ready format) useful. Get it here: https://www.2w2e.com/home/GlobalSoil
These data are described in this recent paper:
Article Global soil, landuse, evapotranspiration, historical and fut...
Best,
Roland.
EDIT: Regarding to @Subhash's answer, I would like to bring to your attention that a new gridded product, GCN250, has been released recently. Find more details in the paper below.
Article GCN250, new global gridded curve numbers for hydrologic mode...
The Africa Soil Information Service (Afsis) have provided digital soil data with spatial information and attributes at 250m resolution. You can check more information and access to the data on thus link