Answer:
I am 52446.
Step-by-step explanation:
Let the digits be a, b, c, d, and e.
Then the number is abcde.
We have five conditions:
(1) a = 5
(2) b = 2
(3) a + b + c + d + e = 21
(4) e = 3, 6, or 9
(5) c = d
From (3), 5 + 2 + c + d + e = 21
7 + c + d + e = 21
c + d + e = 14
From (5), 2c + e = 14
c = ½(14 - e)
If e = 3, c = ½(14 - 3) = 11/2. Not possible.
If e = 9, c = ½(14 - 9) = 5/2. Not possible.
If e = 6, c = ½(14 - 6) = 8/2 = 4.
The solution is
a = 5, b = 2, c = 4, d = 4, e = 6 ⟶ 52446
The number is 52446.