Divisibility RulesReference > Mathematics > Number Theory
How to tell if a number is divisible by a power of two.
Divisibility rules for three, six, and nine
Divisibility rules for five, ten, twenty-five, and one hundred
Lesser known, and much less practical divisibility rules for seven and eleven
Divisibility rule for eleven - alternating digits
Understanding Coronavirus Spread
A Question and Answer session with Professor Puzzler about the math behind infection spread.
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