Number 0...100 to Text

package com.company;

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int number = Integer.parseInt(sc.nextLine());

        if (number >= 0 && number <= 20) {
            if (number == 0) {
                System.out.println("zero");
            } else if (number == 1) {
                System.out.println("one");
            } else if (number == 2) {
                System.out.println("two");
            } else if (number == 3) {
                System.out.println("three");
            } else if (number == 4) {
                System.out.println("four");
            } else if (number == 5) {
                System.out.println("five");
            } else if (number == 6) {
                System.out.println("six");
            } else if (number == 7) {
                System.out.println("seven");
            } else if (number == 8) {
                System.out.println("eight");
            } else if (number == 9) {
                System.out.println("nine");
            } else if (number == 10) {
                System.out.println("ten");
            } else if (number == 11) {
                System.out.println("eleven");
            } else if (number == 12) {
                System.out.println("twelve");
            } else if (number == 13) {
                System.out.println("thirteen");
            } else if (number == 14) {
                System.out.println("fourteen");
            } else if (number == 15) {
                System.out.println("fifteen");
            } else if (number == 16) {
                System.out.println("sixteen");
            } else if (number == 17) {
                System.out.println("seventeen");
            } else if (number == 18) {
                System.out.println("eighteen");
            } else if (number == 19) {
                System.out.println("nineteen");
            } else if (number == 20) {
                System.out.println("twenty");
            }
        }
        String a = null;
        if (number >= 20 && number <= 99) {
            if (number / 10 == 2) {
                a = "twenty";
            } else if (number / 10 == 3) {
                a = "thirty";
            } else if (number / 10 == 4) {
                a = "forty";
            } else if (number / 10 == 5) {
                a = "fifty";
            } else if (number / 10 == 6) {
                a = "sixty";
            } else if (number / 10 == 7) {
                a = "seventy";
            } else if (number / 10 == 8) {
                a = "eighty";
            } else if (number / 10 == 9) {
                a = "ninety";
            }
        }

        String b = null;
        if (number >= 21 && number <= 99) {
            if (number % 10 == 2) {
                b = "two";
            } else if (number % 10 == 3) {
                b = "three";
            } else if (number % 10 == 4) {
                b = "four";
            } else if (number % 10 == 5) {
                b = "five";
            } else if (number % 10 == 6) {
                b = "six";
            } else if (number % 10 == 7) {
                b = "seven";
            } else if (number % 10 == 8) {
                b = "eight";
            } else if (number % 10 == 9) {
                b = "nine";
            } else if (number % 10 == 1) {
                b = "one";
            } if (number % 10 == 0) {
                System.out.println(a);
            } else {
                System.out.println(a + " " +b);
            }


        }


        if (number == 100) {
            System.out.println("one hundred");
        }
        if (number > 100) {
            System.out.println("invalid number");
        }
        if (number < 0) {
            System.out.println("invalid number");
        }
    }
        }