The number 660,000 can be evenly divided by 1 2 3 4 5 6 8 10 11 12 15 16 20 22 24 25 30 32 33 40 44 48 50 55 60 66 75 80 88 96 100 110 120 125 132 150 160 165 176 200 220 240 250 264 275 300 330 352 375 400 440 480 500 528 550 600 625 660 750 800 825 880 1,000 1,056 1,100 1,200 1,250 1,320 1,375 1,500 1,650 1,760 1,875 2,000 2,200 2,400 2,500 2,640 2,750 3,000 3,300 3,750 4,000 4,125 4,400 5,000 5,280 5,500 6,000 6,600 6,875 7,500 8,250 8,800 10,000 11,000 12,000 13,200 13,750 15,000 16,500 20,000 20,625 22,000 26,400 27,500 30,000 33,000 41,250 44,000 55,000 60,000 66,000 82,500 110,000 132,000 165,000 220,000 330,000 and 660,000, with no remainder.
Since 660,000 cannot be divided by just 1 and 660,000, it is a composite number.