+521 is a [natural number](/wiki/natural_number), positioned after 520 and before 522. It stands as a [prime number](/wiki/prime_number), signifying an indivisible quantity in mathematics. Beyond numerical properties, "521" can also denote a specific [year](/wiki/year) in historical records.
+## See also
+- [Prime Number](/wiki/Prime_Number)
+- [Integer](/wiki/Integer)
+- [Number Theory](/wiki/Number_Theory)
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