1 million = 10 lakh = 10,00,000. Likewise, 10 million = 1 crore.

1 billion = 100 crore = 1 arab. So "$5 billion" means 500 crore dollars.

1 trillion = 1 lakh crore = 10 kharab.

The Indian system puts a comma after the first three digits and then every two digits: 1,00,00,000. The international system puts one every three digits: 10,000,000.