A single hamster provides us with 1/2072th of a horsepower[1]. One horsepower is ~745 watt, so if the machine requires 1.21 gigawatt, we need 1 210 000 000 / 745 * 2072 = 3,365,261,744.97 hamsters, provided that we can use the hamsters at 100% efficiency.
[1]http://en.allexperts.com/q/Science-Kids-3250/hamster-science.htm