count occurence of int in db - sql query or array

I'm getting int numbers from one column of a db table, like this for example:
1
13
13
13
56
I want to count which number has the highest occurence - (in this case '13' but in the program I don't know which ID:s are in db). Can I do this with an sql query or do I need to put the id's in an array? I also need to turn the number with the highest occurence into a new variable. Thankful for help!
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