If there is only one character , return the largest prime less than the number
if ( size == 1 ) { ans [ 0 ] = String . fromCharCode ( prevprime [ N [ 0 ] . charCodeAt ( 0 ) - ' ' . charCodeAt ( 0 ) ] + ' ' . charCodeAt ( 0 ) ) ; ans [ 1 ] = ' \0 ' ; return ans ; }