def validate_nhs_number(num):
    s = str(num)
    if len(s) != 10:
        return False

    tot = 0
    for i in range(9):
        dig = int(s[i])
        tot += dig * (10-i)

    tmp = tot % 11
    if tmp == 0:
        checksum = 0
    else:
        checksum = 11 - (tot % 11)

    if checksum == 10 or checksum != int(s[9]):
        return False
    else:
        return True