The minimum length is 4 for Saint Halena (Format: +290 XXXX) and Niue (Format: +683 XXXX). +290 is the country code of Saint Halena and +683 is the country code of Niue. Also both have same International call prefix: 00
The maximum length is 12 for French Guiana, Guadeloupe, Martinique and Reunion having mobile prefix "700". Their mobile length varies (i.e., 9) if the mobile prefix is "6".
French Guiana
Country code : +594
Format : +594 700 XXX XXX XXX
Guadeloupe
Country code : +590
Format : +590 700 XXX XXX XXX
Martinique
Country code : +596
Format : +596 700 XXX XXX XXX
Reunion
Country code : +262
Format : +262 700 XXX XXX XXX
The following link contains the list of different countries, their International calling code, Mobile prefix, National significant number (i.e., the number of digits after the country code excluding any trunk code or access code which is also called as length of the mobile number), and different carriers.