mpichversion: 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/mpich/bin/mpichversion - from package: mpich
/usr/lib/mpich/bin/mpichversion - from package: mpich
/usr/lib64/mvapich2-psm/bin/mpichversion - from package: mvapich2-psm
/usr/lib64/mvapich2/bin/mpichversion - from package: mvapich2
/usr/lib/mvapich2/bin/mpichversion - from package: mvapich2
/usr/lib64/mvapich-psm/bin/mpichversion - from package: mvapich-psm
/usr/lib64/mvapich/bin/mpichversion - from package: mvapich
/usr/lib/mvapich/bin/mpichversion - from package: mvapich

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

On Debian possible default full paths are:

/usr/bin/mpichversion - from package: libmpich-dev

You may install the required package with command apt-get install {package}

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