Python a mathematical solution to the problem

A positive integer n.
It is composed by numeral 3 and 7, and this number, and this number
you figures and multiples are 3 and 7, for the minimum of n
must process.

 

# Coding = UTF-. 8 
Import numpy AS NP 
x_num =. 1
 the while True: 
    x_str = STR (x_num)        # numbers to characters 
    x_str_list = List (x_str)     # to convert the tuple list 
    x_str_len = len (x_str_list) # list element the number 
    x_com x_num =      # for subsequent whether the condition is not satisfied because the number continues to push to cause 
    x_str_list_num Map = (int, x_str_list)     # character array into a digital array 
    sum_x = np.sum (x_str_list_num)             # of an array sum 
    for Word in x_str_list:                  # strings of characters in order to extract 
        IF ((int (Word) == 3or int (Word) ==. 7) and (21 is x_num% == 0) and (0 == 21 is sum_x%) and ( ' . 3 '  in x_str_list) and ( ' . 7 '  in x_str_list)):
             # The number must contain 3 and 7, and the book is a multiple of 21, and the sum of the individual bits in multiples of 3 and 7 
            continue         # continue this cycle 
        the else : 
            x_num = x_num + 21   # If the condition is not satisfied, then, after the digital shift 
            BREAK            # breaks out a loop 
    IF x_com == x_num:         # If you meet the requirements, that is, on a normal cycle for the end, out of the while loop 
        BREAK 
    the else :
         Print(x_num)
         the Continue             # If the condition is not met, the while loop continues 

Print (x_num)

The result: 3333377733 
computational efficiency should be improved