library(terra)
r1 <- rast(ext(61.87125, 76.64458, 23.90153, 37.27042))
r2 <- rast(ext(67.66625, 81.56847, 20.38458, 35.67347))
r3 <- rast(ext(72.64792,84.38125,5.91125,28.13347 ))
( e <- max_extent(r1, r2, r3) )
plot(e, border=NA)
plot(ext(r1), border="red", add=TRUE)
plot(ext(r2), border="green", add=TRUE)
plot(ext(r3), border="blue", add=TRUE)
plot(e, border="black", add=TRUE)
sf::st_bbox(e) # full extent
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