arithchk: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/lib64/mp/bin/arithchk - from package: mp
/usr/lib/mp/bin/arithchk - from package: mp

You may install the required package with command yum install {package}

Error in other languages:
arithchk: bevel nie gevind nie
arithchk: comandă negăsită
arithchk: comando não encontrado
arithchk: commande introuvable
arithchk: command not found
arithchk: käsku ei ole
arithchk: không tìm thấy lệnh
arithchk: komanda nerasta
arithchk: Kommando nicht gefunden.
arithchk: kommandot finns inte
arithchk: komut yok
arithchk: nie znaleziono polecenia
arithchk: níor aimsíodh an t-ordú
arithchk: no se encontró la orden
arithchk: no s'ha trobat l'ordre
arithchk: opdracht niet gevonden
arithchk: parancs nem található
arithchk: perintah tidak ditemukan
arithchk: príkaz nenájdený
arithchk: příkaz nenalezen
arithchk: команда не найдена
arithchk: командата не е открита
arithchk: 命令找不到
arithchk: コマンドが見つかりません