You should have learned how to round off numbers in primary school. In case you slept thought that lesson, hereâ€

As for definitions, Wikipedia says that a round number is â€œa number that ends with one or more zeroes (0), meaning that they are multiples of 10, 100, 1000, and so onâ€, and notes that some variations “allow multiples of 5 or 25 to be also considered round.”

Wolfram Math World definition is a tad more involved. According to these guys:

- A round number is a number that is the product of a considerable number of comparatively small factors (Hardy 1999, p. 48);
- Round numbers are very rare. As Hardy (1999, p. 48) notes, “Half the numbers are divisible by 2, one-third by 3, one-sixth by both 2 and 3, and so on. Surely, then we may expect most numbers to have a large number of factors. But the facts seem to show the opposite.”
- A positive integer
*n*is sometimes said to be round (or “square root-smooth”) if it has no prime factors greater than the square root of*n*. The first few such numbers are 1, 4, 8, 9, 12, 16, 18, 24, 25, 27, 30, 32, … (Sloane’s A048098). Using this definition, an asymptotic formula for the number of round integers less than or equal to a positive real number x is given by

Huh?

Definitions aside, we love round number so much that we always expect great things to happen in the years with round numbers. Hereâ€*you*!