Richards, who held the record for the quickest hundred in Tests off 56 balls jointly with Pakistan's Misbah-ul-Haq till McCullum broke it yesterday, was all praise for the Kiwi skipper for his record-breaking feat.
"Let me take this opportunity to congratulate Brendon...(I've) been a great fan of yours for many years. Well done on your achievement," said Richards in the video on Twitter, posted by Pakistan Super League (PSL) side Quetta Gladiators.
McCullum came to bat when New Zealand were struggling at 32 for three on the opening day of the first Test against Australia at Christchurch.
McCullum smashed 100 runs off just 54 deliveries to pull New Zealand out of trouble and in the process also broke Richards' record set against England in 1986.