Printable prime number chart, 1 to 100
A hundred square with the twenty-five prime numbers below 100 shaded and the other seventy-five cells printed plain. One A4 sheet, fifteen point.
What this sheet holds
The chart is a hundred square, ten columns by ten rows, carrying the whole numbers from 1 to 100 at fifteen point inside twenty-two ruled lines. Twenty-five of the hundred cells are shaded and the remaining seventy-five are printed plain.
A prime number is a whole number greater than one whose only whole divisors are itself and one. Exactly twenty-five of the numbers from 1 to 100 answer to that: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89 and 97. Those twenty-five are the shaded cells. The number 1 is not among them, because the definition asks for a number greater than one, so 1 sits in the top left corner unshaded.
Taking the sheet
PDF, PNG or SVG, drawn in your browser as you ask for it, with nothing uploaded and nothing kept. The shading is a setting, so you can change which numbers are picked out, alter the range, choose the paper, turn the sheet on its side, or empty the cells altogether.
How the shading falls across the grid
Two things are visible at once on this sheet, and both are worth stating in numbers rather than impressions. The first is that the shaded cells thin out as the numbers grow. The top row carries four of them, 2, 3, 5 and 7. The second row carries four again, 11, 13, 17 and 19. The bottom row, 91 to 100, carries one: 97.
The second is that after 2 every shaded cell is odd. Any even number above 2 has 2 as a divisor besides itself and one, so it fails the definition immediately, and 2 is the only even number that survives it.
Because the grid is ten cells wide, a column is a run of numbers that all end in the same digit, and that turns the odd rule into something you can see by column. The column ending in 0 carries no shaded cell at all, and neither do the columns ending in 4, 6 or 8. The column ending in 2 carries exactly one, 2 itself, at the very top. The column ending in 5 carries exactly one, 5, also at the top. Everything else that is shaded, twenty-three cells of the twenty-five, stands in the four columns ending in 1, 3, 7 and 9. Seven of them are in the column ending in 3 and five are in the column ending in 9.