Number theory is a branch of mathematics that deals with the properties of positive integers (1, 2, 3, 4, 5, …). In number theory, numbers are classified into different types, such as natural numbers, whole numbers, complex numbers, and so on. The sub-classifications of the natural number are given below:
- Even Numbers: The numbers that are evenly divided by 2 are called even numbers (2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26 . . .).
- Odd Numbers: The numbers that are not evenly divided by 2 are called odd numbers (1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23 …..).
- Square Numbers: A number multiplied by itself is called square numbers (4, 9, 16, 25, 36, 49, 64, 81,100, 121, 144 . . .).
- Cube Numbers: A number multiplied by itself 3 times is called cube numbers (8, 27, 64, 125, 216, 343, 512, 729, 1000 . . .).
- Prime numbers: If a number has only two factors: 1 and the number is called prime numbers (2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47,53, 59, 61 . . .).
- Composite Numbers: Composite number has more than two factors. The composite numbers are numbers that are not prime numbers. The number 1 is neither prime nor composite (4, 6, 8, 9, 10, 12, 14, 15, 16,18, 20, 21, 22, 24 . . .).
- Modulo 4 Numbers: A number is said to be 1 (modulo 4 ) number if it leaves a remainder 1 when divided by 4. Similarly, if a number leaves a remainder 3 when divided by 4, it is said to be 3 (modulo 4) number (1, 5, 9, 13, 17, 21, 25, . . .).
- Triangular Numbers: A number is said to be a triangular number when that number of pebbles can be arranged in a triangle using one pebble at the top, two pebbles in next row, three pebbles in next row and so on (3, 6, 10, 15, 21, 28, 36, 45,. . .).
- Fibonacci Numbers: Fibonacci numbers are created starting with 1 and 1, then get the next number in the list and adds the previous two numbers. Say, 1+1 =2, and then add 1+2 you get 3, then adding 2+3 gives 5, then 3+5 gives 8, and so on.