Google+ profile id is specific id allocates different id to every one,it is also used to create the google+ widgets and goolge+ buttons.The way to get your google+id is go to googleplus and in the top menu go to profile you can see below image on your profile and click on the marked tab as in the image.
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After clicking there you can see the some number id on the url locations seen in the below image.
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After clicking there you can see the some number id on the url locations seen in the below image.