$f:\mathbb{N}\rightarrow \mathbb{N}$ is a one-to-one function such that $f(mn)=f(m)f(n).$ Find the lowest possible value of $f(999)$.
62111
Functional Equation $f(mn)=f(m)f(n)$.
118154
$f: \mathbb{R} \to \mathbb{R}$ that takes each value in $\mathbb{R}$ twice
27859
least common multiple of $\{1,2,...,n\}$ is bigger than $2^{n-1}$
65162
Show that $\dim H^0(\mathbb{P}^n, \mathcal{O}_{\mathbb{P}^n}(m)) = {n + m \choose n}$ if $m \geq 0$, and $0$ otherwise.
33144
Criterion for $\phi(mn)=m\phi(n)$ to be true
1071
Determine all functions $f:\mathbb{N}\rightarrow\mathbb{N}$ such that $xf(y)+yf(x)=(x+y)f(x^2+y^2)$ for all $x,y\in\mathbb{N}$ (contest question)
128766
Show that the set of functions $\mathbb{N}\to\{0,1\}$ is not countable
10477
Finding the closure of A=$\mathbb Q \cap [0,1]$.
126367
Let $p$, $q$ be prime numbers such that $n^{3pq} – n$ is a multiple of $3pq$ for all positive integers $n$. Find the least possible value of $p + q$.
21986
What is the minimum value of $(1 + a_1)(1 + a_2). . .(1 + a_n)$?
84143
Given any function $g(x): \mathbb{R} \rightarrow \mathbb{R}$, find a function $f(x)$ such that $f(f(x)) = g(x)$.
102764
Let $f(x)=\int_0^1|t-x|t~dt$ for all real $x$. Sketch the graph of $f(x)$, what is the minimum value of $f(x)$
144473
Finding all functions $ f : \mathbb N^*\to\mathbb N^*$ such that for every $ x , y \in \mathbb N ^ * $, $ f ( x ) + f ( y ) \mid x ^ n + y ^ n $
32525
If $f(1)=1$, then is it true that $f(n)=n$ for all $n \in \mathbb{N}\cup\{0\}$.
78471
Closure of $\{\frac{1}{n}\}:=M$
5375
Is there a bijective function mapping Natural numbers to Natural numbers, other than $f(n) = n$?
135511
$M_a =\{ f\in C[0,1] |\ f(a)=0 \}$ for $a$ $\in$ $[0,1]$. Is $M_a$ finitely generated in $C[0,1]$?