How to interpret the question: "How many elements from the set $\mathbb{Z}/42\mathbb{Z}$ satisfy $x^2=x$?"
3563
Find all roots of $\,x^2\!\equiv x\pmod{\!900}$, i.e all idempotents in $\Bbb Z_{900}$
80551
Find Units in $\mathbb{Z}[\sqrt{n}]$
50412
Prime elements in $\mathbb{Z}/n\mathbb{Z}$
86807
The units of $\mathbb Z[\sqrt{2}]$
5297
If G is a finite abelian group and $a_1,...,a_n$ are all its elements, show that $x=a_1a_2a_3...a_n$must satisfy $x^2=e$.
137010
What are integers $x$ and $n$ such as $ x^4+x^3+x^2+x+1 = n^2$?
39492
Finding $z\in \mathbb C$ with $\sin z = 2$?
120181
The ideal generated by $2$ and $ x$ in $\mathbb{Z}[x]$
134050
Question about set notation: what does $]a,b[$ mean?
132470
Does $\mathbb R^2$ contain more numbers than $\mathbb R^1$?
128566
Proving $2$ generates $(\mathbb{Z}/19\mathbb{Z})^*$ by only looking at a few powers
117392
Does $x^2 - y^2 = 12345678$ (x,y are integers) have any solutions?
56574
For any integer $a,b$ let $N_{a,b}$ denote the number of positive integer $x<1000$ satisfying $x= a( mod\;27)$ and $x=b(mod\;37)$. Then
41731
Question about the order of the product of two elements in an abelian group
68915
What are the units in $\mathbb{Z}[\root 3 \of 2]$?
15604
Determine the set of points $z$ that satisfy the condition $|2z|>|1+z^2|$
109968
Let $X= \{ A \subset \mathbb{N} : \mathbb{N} \backslash A \text{ is finite}\}$. What is the cardinality of $X$? Prove it.