hilbert: 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/lib64/4ti2/bin/hilbert - from package: 4ti2

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

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