Add all the proper divisors of 6 and you get 6 again
If you add the proper divisors of 6 (1, 2, and 3), you get 1+2+3=6, exactly the original number! Numbers like this are called perfect numbers. Enter a number to check whether it is perfect, deficient, or abundant.
Three classifications: If the sum of the proper divisors is less than the number, it is deficient; if it is equal, it is perfect; if it is greater, it is abundant. Perfect numbers are very rare — 6, 28, 496, 8128... and the next one jumps all the way to 33,550,336!
Numbers 1–200 at a glance
Perfect Abundant Deficient
💡 It was proved long ago that every even perfect number has the form 2ⁿ⁻¹×(2ⁿ−1), when 2ⁿ−1 is prime. But no one knows whether any odd perfect number exists — it remains a long-standing unsolved problem in mathematics.