The first prime number is 2, but 2 doesn't divide into 1225 evenly (no remainder).
The next prime number is 3, but 3 doesn't divide into1225 evenly either.
The next prime number is 5 and it does divide into 1225 evenly:
1225 ÷ 5 = 245
245 ÷ 5 = 49
But 49 = 7 x 7; so all the factors of 1225 are 5 (twice) and 7 (twice).
1225 = 5 x 5 x 7 x 7