Any natural number can be expressed as a product of its prime factors. A prime factor of x is a prime number that perfectly divides x (so that the rest is equal to 0). In our case, 1386 = 2*3*3*7*11. You can get this result by trying to divide the number (1386) by 2, 3, 5, 7, 11 and so on. Every time you successfully divide it by a prime number (starting from 2), you use the result you obtain and try to divide it using the same strategy. When the current number can no longer be divided by a prime number, you go to the next prime number and try to divide it by that number. At the end you multiply the prime numbers you managed to divide your number by.