A number is odd if it is not divisible by 2.
The number 1,564,845,663 is odd, because it is not divisible by 2: the remainder is 1 when divided by 2.
How to recognize an odd number: its last digit, the one that is in the ones place (the first digit of the number counted from the right), is: 1, 3, 5, 7 or 9.
Mathematically, the odd numbers can be written as:
2 × k + 1, where k ∈ Z, the set of integer numbers
The number 1,564,845,663 is odd.
Operating rules (scroll down...)
When working with even and odd numbers, the following rules apply:
Addition:
even + even = even; even + odd = odd; odd + odd = even
Examples:
2 + 4 = 6 (even); 1 + 2 = 3 (odd); 1 + 3 = 4 (even).
Subtraction:
even - even = even; even - odd = odd; odd - odd = even
Examples:
4 - 2 = 2 (even); 2 - 1 = 1 (odd); 3 - 1 = 2 (even).
Multiplying:
even × even = even; even × odd = even; odd × odd = odd
Examples:
2 × 4 = 8 (even); 2 × 3 = 6 (even); 3 × 5 = 15 (odd).