Even, Odd, Prime and Composite Numbers
Even and Odd: Any integer which is divisible by two is called an even number. Any integer which is not divisible by two is called an odd number.
N.B.: Zero has not been categorized in either of the two categories.
Prime and Composite : Any integer which is divisible by 1 and itself only is called a prime number. All integers which are not prime are called composite number as they are composed of two or more prime numbers.
N.B.: 1 is not a prime number.
Positive and negative: Any number which is greater than 0 is positive. Any number less than that is negative.
Perfect numbers:- If the sum of the divisors of N, excluding N itself, is equal to N, then N is called a perfect number. e.g. 6, 28, 496, 8128 etc.
6 = 1 + 2 + 3;
28 = 1 + 2 + 4 + 7 + 14;
496 = 1 + 2 + 4 + 8 + 16 + 31 + 62 + 124 + 248.