Find the smallest natural number n which satisfies 1 n20 2 T

Find the smallest natural number n which satisfies

1) n>20

2) The sum of the proper divisors of n is n-1

Solution

1)n>20

the very next natural number is 21

so n=21 is the smallest natural number that satisfies n>20

2)The sum of the proper divisors of n is n-1

here n=6

proper divisors of 6 is 2,3

sum=2+3=5=6-1