What is the minimum length of a valid international phone number?

I need to validate user input of an international phone number. According to E.164, the maximum length is 15 digits, but I was unable to find any information about the minimum. I consider digits only, no plus sign or separators.

Solution 1:

As per different sources, I think the minimum length in E-164 format depends on country to country. For eg:

• For Israel: The minimum phone number length (excluding the country code) is 8 digits. - Official Source (Country Code 972)

• For Sweden : The minimum number length (excluding the country code) is 7 digits. - Official Source‎ (country code 46)

• For Solomon Islands its 5 for fixed line phones. - Source (country code 677)

... and so on. So including country code, the minimum length is 9 digits for Sweden and 11 for Israel and 8 for Solomon Islands.

Edit (Clean Solution): Actually, Instead of validating an international phone number by having different checks like length etc, you can use the Google's libphonenumber library. It can validate a phone number in E164 format directly. It will take into account everything and you don't even need to give the country if the number is in valid E164 format. Its pretty good! Taking an example:

String phoneNumberE164Format = "+14167129018"
PhoneNumberUtil phoneUtil = PhoneNumberUtil.getInstance();
try {
    PhoneNumber phoneNumberProto = phoneUtil.parse(phoneNumberE164Format, null);
    boolean isValid = phoneUtil.isValidNumber(phoneNumberProto); // returns true if valid
    if (isValid) {
        // Actions to perform if the number is valid
    } else {
        // Do necessary actions if its not valid 
    }
} catch (NumberParseException e) {
    System.err.println("NumberParseException was thrown: " + e.toString());
}

If you know the country for which you are validating the numbers, you don;t even need the E164 format and can specify the country in .parse function instead of passing null.

Solution 2:

The minimum length is 4 for Saint Helena (Format: +290 XXXX) and Niue (Format: +683 XXXX).