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Divisibility Rules 1 to 20: The Complete List With Examples
Divisibility rules for 1 to 20 in one chart. Learn the quick test for each divisor, why the digit-sum and alternating-sum rules work, and how each rule reveals the remainder.
Read More →What Does a Remainder of 0 Mean? No Remainder Explained
A remainder of 0 means the dividend is exactly divisible by the divisor. Learn what no remainder means, why it makes the divisor a factor, and where a zero remainder matters.
Read More →How to Check if a Number Is Prime: Prime Test by Division
To check if a number is prime, test every divisor from 2 up to its square root for a remainder of 0. Learn the trial division method, the square root shortcut, and a code test.
Read More →Modulo in Python, JavaScript and C: A Language Comparison
The % operator behaves differently across languages. Compare modulo in Python, JavaScript, C, Java and more, with a behaviour table, negative-number results and portable code patterns.
Read More →Modulo Operator Explained: What Is Modulo and How Mod Works
The modulo operator returns the remainder of a division. Learn what modulo means, how the mod operator works in code, its precedence, negative-number behaviour and real uses in one guide.
Read More →Remainder of Negative Numbers: Why -7 mod 3 Is 2 or -1
The remainder of a negative number has two valid answers. Learn why -7 mod 3 gives 2 in Python and -1 in C, how floored and truncated division decide the sign, and which to use.
Read More →How to Find the Remainder: 5 Methods With Worked Examples
The remainder is what stays behind after division. Learn 5 methods to find the remainder by hand, on a calculator, and in code, with the formula, examples and practice problems.
Read More →Long Division With Remainders: Step-by-Step Method
Long division with remainders solved digit by digit. Learn the divide-multiply-subtract-bring down cycle, handle internal zeros and decimals, and check every answer with the remainder formula.
Read More →Remainder Shortcuts and Tricks: Find the Remainder Fast
Find the remainder quickly without long division. Learn the shortcuts for dividing by 2, 5, 9, 10 and 11, the power cycle trick for exponents, and the bitwise method for powers of 2.
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