wordpress error

it shows this code after i activating it

Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 20480 bytes) in /home/hitzcomn/public_html/wp-includes/meta.php on line 1071

Notice: is_page was called incorrectly. Conditional query tags do not work before the query is run. Before then, they always return false. Please see Debugging in WordPress for more information. (This message was added in version 3.1.0.) in /home/hitzcomn/public_html/wp-includes/functions.php on line 5663

Notice: is_singular was called incorrectly. Conditional query tags do not work before the query is run. Before then, they always return false. Please see Debugging in WordPress for more information. (This message was added in version 3.1.0.) in /home/hitzcomn/public_html/wp-includes/functions.php on line 5663

Notice: is_embed was called incorrectly. Conditional query tags do not work before the query is run. Before then, they always return false. Please see Debugging in WordPress for more information. (This message was added in version 3.1.0.) in /home/hitzcomn/public_html/wp-includes/functions.php on line 5663

Notice: is_search was called incorrectly. Conditional query tags do not work before the query is run. Before then, they always return false. Please see Debugging in WordPress for more information. (This message was added in version 3.1.0.) in /home/hitzcomn/public_html/wp-includes/functions.php on line 5663
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