Zero (0) has been used in mathematics for over 2,000 years. Mathematically, it is an even number: it can be divided by two to create a whole number (0) and it has odd numbers either side of it (-1 and 1). And even today, a sense of mystery surrounds the zero.
If you are playing roulette in a casino and place all your money on Even – you will only get half your stake back if the ball lands on zero. On US Navy vessels, compartments are divided into even-sides (port) and odd-sides (starboard); zero compartments are placed down the centre (eg 6420135). Ask someone if zero is odd or even and they might hesitate, like the gendarmes in Paris, in 1977. At that time, smog had led to odd/even car restrictions in the capital – cars with licence plates ending in odd numbers were allowed to drive on odd-numbered days and vice versa – but police were unsure whether to stop and fine zero-numbered plated cars for driving on odd-numbered days, because they weren't clear on the status of the zero.
Where a zero is used to denote the absence of a number, this again can cause confusion. The Italian mathematician Fibonacci classified the zero as a 'sign', not a number. But it could be argued that zero is the most even of all numbers – however many times you divide it by two, it will always equal a whole number (0).
Without the zero, a place value system for numbers would not be possible and, neither in consequence, would Kakuro puzzles. With that fact alone in mind, let's be thankful for zero (as opposed to nothing).