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<p>An element of a ring that is equal to its own square is called an <a href="page.php?w=idempotent_%28ring_theory%29">idempotent</a>. In any ring, 0 and 1 are idempotents. There are no other idempotents in fields and more generally in <a href="page.php?w=integral_domain">integral domain</a>s. However, the ring of the integers <a href="page.php?w=modular_arithmetic">modulo</a>&nbsp; has  idempotents, where  is the number of distinct <a href="page.php?w=integer_factorization">prime factors</a> of&nbsp;.A commutative ring in which every element is</p><p>
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