Is there any algorithm which check right NPI (National Provider Identification) number?

Question

Basically I'm developing application using asp.net and I want to write Custom validator which will check right NPI number.

Answer 1

Wikipedia says:

A 10-digit NPI Number may be validated using the Luhn algorithm by prefixing "80840" to the 10-digit number.

Obviously that just validates the check digit. To find whether a number is actually assigned, I think you need a list. There's an online lookup, for example. Even without that, there may be additional checks you can do if you know anything about how HIPAA hands the numbers out.

Answer 2

In case someone has found this post but is looking for this in Java, here is a java program that does this:

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class NpiUtil {
    private static final String NPI_PATTERN_STRING = "[0-9]{10}";
    private String npi;

    public static boolean isValidNpi(final String npi) {
        return new NpiUtil(npi).isValid();
    }

    private static String fromCharCode(int... codePoints) {
        return new String(codePoints, 0, codePoints.length);
    }

    public static String generateRandomNpi() {
        Double randomNumber = Math.floor(Math.random() * (999999999 - 100000000 + 1) + 100000000);
        int tmp;
        int sum;
        int i;
        int j;
        String npi9 = String.valueOf(randomNumber.intValue());
        i = npi9.length();
        if ((i == 14) && (npi9.indexOf("80840", 5) == 0))
            sum = 0;
        else if (i == 9)
            sum = 24;
        else {
            return "!";
        }

        j = 1;
        while (i != 0) {
            tmp = npi9.charAt(i - 1) - new String("0").charAt(0);
            if ((j++ % 2) != 0) {
                if ((tmp <<= 1) > 9) {
                    tmp -= 10;
                    tmp++;
                }
            }
            sum += tmp;
            i--;
        }
        String checkDigit = fromCharCode(((10 - (sum % 10)) % 10 + 48));
        return randomNumber.longValue() + checkDigit;
    }

    private NpiUtil(final String npi) {
        this.npi = npi.trim();
    }

    private boolean isValid() {
        return this.npi.length() == 10 && this.complies();
    }

    private boolean complies() {
        if (!this.npi.matches(NPI_PATTERN_STRING)) {
            return false;
        }
        final Character lastDigit = this.npi.charAt(9);
        final List<Integer> everyOther = this.listWithEveryOtherDoubled(this.npi.substring(0, 9));
        int sum = 0;
        for (final Integer num : everyOther) {
            sum += sumOfDigits(num);
        }
        final int total = sum + 24;
        final int units = total % 10;
        final int checkDigit = (units != 0) ? (10 - units) : units;
        return Character.getNumericValue(lastDigit) == checkDigit;
    }

    private List<Integer> listWithEveryOtherDoubled(final String str) {
        final List<Integer> nums = new ArrayList<Integer>();
        for (int i = 0; i < str.length(); ++i) {
            if (i % 2 == 0) {
                nums.add(2 * Character.getNumericValue(str.charAt(i)));
            } else {
                nums.add(Character.getNumericValue(str.charAt(i)));
            }
        }
        return nums;
    }

    private static int sumOfDigits(final int number) {
        int num = number;
        int sum = 0;
        while (num > 0) {
            sum += num % 10;
            num /= 10;
        }
        return sum;
    }

    public static void main(final String[] args) {
        System.out.println("Hello, World!");
        System.out.println("1234567890".matches(NPI_PATTERN_STRING));
        System.out.println("123456789".matches(NPI_PATTERN_STRING));
    }
}

Usage:

import org.junit.Assert;
import org.junit.Test;

public class NpiUtilTest {
    @Test
    public void testNpiUtil() {
        for (int i = 0; i < 100; ++i) {
            Assert.assertTrue(NpiUtil.isValidNpi(NpiUtil.generateRandomNpi())); 
        }
    }
}