What are the factors of 15900
well, certainly 10* 10 * 159 = 5*2*5*2 * 159
now what can you do with 159?
try 3
3 * 53
what can you do with 53?
nothing :(
so
2*2*5*5*3*53
now what can you do with 159?
try 3
3 * 53
what can you do with 53?
nothing :(
so
2*2*5*5*3*53