Playing with Numbers 🧮

Instead of dividing to check, a divisibility rule lets you tell instantly. And breaking any number down into its prime building blocks unlocks HCF and LCM without listing endless factors.

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Part 1 · Divisibility Rules

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Part 2 · Prime Factorization

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Part 3 · HCF & LCM

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Mock Test

Divisibility Rules ✅

Check the last digit, the last few digits, or the digit sum — no long division needed.

Divisible by	Rule
2	last digit is even (0,2,4,6,8)
3	sum of digits is divisible by 3
4	last 2 digits divisible by 4
5	last digit is 0 or 5
8	last 3 digits divisible by 8
9	sum of digits is divisible by 9
10	last digit is 0
11	(sum of digits at odd places) − (sum at even places) is 0 or divisible by 11

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Game 1 — Is It Divisible?

Prime Factorization 🌳

Every number bigger than 1 can be broken down into a unique set of prime numbers, multiplied together.

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Game 2 — Match the Prime Factorization

HCF & LCM by Prime Factorization 🤝

Once both numbers are broken into primes, HCF takes the common ones and LCM takes every prime that appears, at its highest power.

🪜 The method

Write both numbers as a product of primes.
HCF = multiply only the primes common to both, using the smaller power.
LCM = multiply every prime that appears in either number, using the larger power.

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Game 3 — Find the HCF and LCM

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Game 4 — Odd One Out

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Playing with Numbers Mock Test

12 IMO-style questions on divisibility, primes, HCF and LCM. 🍀

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Whole Numbers 🔵

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