How fast should a Python factoring script be?

Just how efficient is "good enough" for all intents and purposes? I wrote a script to simply list off all numbers that divide into an input, x, as pairs (i, n//i) and was just curious how efficient I should be going for? what is the acceptable rate at which the script starts to lose its efficiency? This is my code (although advice is appreciated, I just want to give an idea as to how it works).

import time
print('''This program determines all basic factors of a given number, x, as ordered            pairs, (a, b) where ab=x.
Type "quit" to exit.''')

timer = input('Would you like a timer? (y/n) ')
while  1:
    try:
        x =(input('x = '))                                               
        T0 = time.time()
        b = []
        n = int(x)**0.5
        ran = list(range(1, int(n)+1))
        if int(x) % 2 == 1:                                          
            ran = ran[::2]
        for i in ran:
            if int(x) % i == 0:
                m = (i, int(x)//i)
                b.append(m)
        else:
            pass
    except ValueError as error_1:
        if x == 'quit':
            break
        else:
            print(error_1)
    except EOFError as error_2:
        print(error_2)
    except OverflowError as error_3:
        print(error_3)
    except MemoryError as error_4:
        print(error_4)
    T1 = time.time()
    total = T1-T0
    print(b)
    print(str(len(b)) + ' pairs.')
    if timer == 'y':
    print("%.5f" % total + ' seconds.')

some of the results are:

x = 9
[(1, 9), (3, 3)]
2 pairs.
0.00000 seconds.

x = 8234324543
[(1, 8234324543)]
1 pairs.
0.07404 seconds.

x = 438756349875
[(1, 438756349875), (3, 146252116625), (5, 87751269975), (15, 29250423325), (25,         17550253995), (75, 5850084665), (125, 3510050799), (375, 1170016933), (557, 787713375),   (1671, 262571125), (2785, 157542675), (8355, 52514225), (13925, 31508535), (41775,   10502845), (69625, 6301707), (208875, 2100569)]
16 pairs.
0.88859 seconds.

So this program can be pretty quick, but then the speed drops rather rapidly once you get up to higher numbers. Anyways, ya, I was just wondering what is considered acceptable by todays standards?