Number Explorer

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100 numbers from 1 to 100, each coloured by its most interesting property. Numbers can belong to multiple categories — click a legend badge to highlight just that group.

Prime Perfect Square Fibonacci Triangular Perfect Power of 2

What is this?

The Number Explorer lets you investigate number types — primes, composites, factors, multiples, and perfect squares — and discover the patterns that make mathematics work.

Why does it matter?

Number theory is the foundation of cryptography (the security behind every website and bank), algorithms, and all higher mathematics including algebra and calculus.

Key terms

Prime — a number with exactly two factors: 1 and itself (2, 3, 5, 7, 11…) Composite — a number with more than two factors (4, 6, 8, 9, 10…) Factor — a number that divides evenly into another with no remainder Multiple — the result of multiplying a number by any whole number Square number — a number produced by multiplying an integer by itself (1, 4, 9, 16…) Perfect number — equals the sum of its proper divisors (6 = 1+2+3)

🎯 Try this challenge

Is 97 a prime number? Enter it in the explorer and check. Now try 91 — is it prime or composite? What is its smallest prime factor? Hint: try dividing by 7.

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