He co-created Spider-Man and Dr Strange...
...but this is Steve Ditko's first co-creation (with writer Joe Gill), exactly as it appeared in Space Adventures #33 (1960)!
Captain Atom has enjoyed the longest career of any Charlton character, still going today in his own title (from DC)! (Note: The Charlton version of the Blue Beetle didn't come along until 1964, and the Ditko-revised version first appeared in 1967!)
Note that despite the blue/silver coloring on the interiors, Captain Atom was shown on the cover in his orange/yellow garb.
Also, his trademark hair-color change from red to white when he "powers up" isn't shown.