Most of which aren't currently in service.
Russia and other powers certainly keep a lot of older tanks in reserve condition, but the number of main battle tanks is huge. Here are just the countries that have more than 1,000:
China has 9150
USA has 8848
India has 6464
Egypt has 4624
Syria had 4500
North Korea 4200
Israel 4170
Turkey3778
Pakistan 2924
Ukraine had 2809
South Korea 2381
Taiwan 2000
Belarus 1665
Iran 1658
Greece 1556
Vietnam 1470
Yemen had 1260
Jordan 1250
Morocco 1215
Saudi Arabia 1210
Poland 1009