Have only just started learning Python and to practice what i have learned so far i wrote this:

Code:
#!/usr/bin/python
i = 'Skype'
j = 46,178,617
x = 'VOIP'
Z = "Making it a market leader in it's field."

print "%s is an online %s product." % (i, x)
print "It has over %d million regular user's daily." % j
print "Making %s a market leader in it's field." % i
But when i try to run it i get the following error:

Skype is an online VOIP product.
Traceback (most recent call last):
File "./more_practice.py", line 8, in <module>
print "It has over %d million regular user's daily." % j
TypeError: not all arguments converted during string formatting

I am convinced that the problem is down to the variable, j = 46,178,617 because it is such a large number. So could someone tell me how i can display the contents of the variable correctly please.