5 - Number of double-hundreds hit by Joe Root in Tests. Among England batsmen, only Wally Hammond has more such scores with seven. Root's predecessor as England captain, Alastair Cook, also hit five such scores.
3 - Number of double-hundreds by Root as captain - two more than any other batsman to lead England in Tests. Click here for a list of England captains to hit double-centuries in Test cricket.
2010 - The last time a visiting batsman hit a double-hundred in Tests in India, before Root in Chennai. Brendon McCullum had hit 225 on that previous occasion, in Hyderabad. McCullum was also the last one to notch up a double-century against India in Tests. He hit 302 in the second innings of the Wellington Test in 2013-14. Click here for a list of double-hundreds (and triples) against India.
2 - Number of England batsmen to score more runs in Tests than Root. Root passed Alec Stewart in this innings. Click here for a list of top run-scorers for England in Tests.
22 - Number of Tests since Root's average was last in the fifties. The previous time before this match that his average was above 50 was at the end of Colombo Test in 2018-19. In two calendar years since, then Root had averaged just 38.67, before hitting the rich vein of current form.
644 - Runs scored by Root in his last-three Tests. Only two other batsmen from England - Hammond and Graham Gooch - have scored more runs than Root in three successive Tests. Hammond racked up 779 runs in three Tests against Australia in 1928-29. Gooch scored 763 runs in 1990 - 122 at Lord's and 184 at Edgbaston against New Zealand, before amassing 456 runs at Lord's against India in the next Test. Root potentially has one more innings in this match left to add to his total. Note: Only the highest aggregate for each batsman in a three-match sequence is mentioned here.
210 - The previous highest Test score by a visiting batsman at Chepauk, Chennai, which was by Dean Jones - in the famous tied Test in 1986. Root scored 218. His double-hundred was only the fifth by a visiting batsman on this ground and the first in nearly 20 years since Matthew Hayden's 203.