A perfect number is a natural number equal to the sum of all its own divisors (that is, of all positive divisors other than the number itself). As natural numbers increase, perfect numbers are encountered less and less. Perfect numbers form a sequence: 6, 28, 496, 8128, 33550336 .....The 1st perfect number - 6 has the following proper divisors: 1, 2, 3; their sum is 6. The 2nd perfect number - 28 has the following own divisors: 1, 2, 4, 7, 14; their sum is 28. The third perfect number - 496 has the following own divisors: 1, 2, 4, 8, 16, 31, 62, 124, 248; their sum is 496. The 4th perfect number - 8128 has the following own divisors: 1, 2, 4, 8, 16, 32, 64, 127, 254, 508, 1016, 2032, 4064; their sum is equal to 8128.

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