50,000 is a popular number. I guess that’s the standard number for today’s (and previous years) Basij army.
~
youtube.com/watch?v=3dQGQ1X-hSM
Video Description - SNIPPET - quote:
Addressing a massive parade by 50,000 members of Iran’s Basij forces, the commander stressed on Friday that the country would respond to any threat with full force.
He added that if the US and Israel really want to Iran, they should be prepared to pay the price.
~
uskowioniran.com/2008/11/jafari-addresses-basij.html
SNIPPET - quote: “From Mehr News Agency
Islamic Revolution Guards Corps Commander Major General Mohammad Ali Jafari on Tuesday emphasized that the enemies will never dare to invade Iran because of Basij forces.
“Even if the enemies surrounded the country, they would not dare to even utter a threat against Iran,” he told 50,000 Basij forces at a gathering in Khorasan Razavi Province.”
(February 25, 2008)
The YouTube video in post no. 18 was posted in 2011.