10001 and in general $10^k + 1$, how can we identify without brute force that such numbers are not prime?
33177
All numbers of form $10^{k} + 1$ are composite for $k{\gt}2$ proof
132928
Digits of $\pi$ forming primes?
101987
Is there possibly a largest prime number?
76807
How come if $\ i\ $ not of the following form, then $12i + 5$ must be prime?
78342
When is $\phi(n)$ a prime number?
146066
Fastest way to find if a given number is prime
131385
How to provide a counterexample for if $n$ is prime, then $2^n -1$ is prime
134963
Proving a non-prime (composite) number $> 1$ has a divisor $d \leq\sqrt q$
98468
Are there infinitely many primes of the form $n!+1$?
72406
Last two digits of $2^{1000}$ via Chinese Remainder Theorem?
49649
How can I find out whether a number is a quadratic residue in a large modulo?
155937
The reciprocal of many prime numbers p in base 10 have a set of repeating digits p-1. Why?
79208
Is the number $-1$ prime?
66623
Primes dividing $11, 111, 1111, ...$
48884
Determine whether $712! + 1$ is a prime number or not
46946
Is there an elementary proof that $\sum \limits_{k=1}^n \frac1k$ is never an integer?
68068
For any integer n greater than 1, $4^n+n^4$ is never a prime number.