It's about 0.00000002 times as long as Pius IX's reign.
In other words, 21.340 seconds is 0.000000021370 times the length of Pius IX's reign, and the length of Pius IX's reign is 46,790,000 times that amount.(a.k.a. Pope Blessed Pius IX, a.k.a. Giovanni Maria Mastai-Ferretti) (1792-1878)
The longest reigning Pope in the Church's history, Pius IX reigned from June 16th, 1846 to February 7th, 1878 — 998,700,000 seconds. As the last monarchical Pope, he ruled over 3,000,000 subjects in the Papal States until 1870.
It's about 0.000000007 times as long as Pepi II's reign.
In other words, 21.340 seconds is 0.00000000700 times the length of Pepi II's reign, and the length of Pepi II's reign is 100,000,000 times that amount.(a.k.a. Neferkare) (2278 BCE - 2184 BCE)
The sixth dynasty pharaoh of Egypt's Old Kingdom, Pepi II Neferkare ascended to the throne at the age of six and is generally thought to have reigned until his death at the age of one-hundred — a total of 3,000,000,000 seconds. His reign was the longest of any monarch in history.
It's about 0.000000003 times as long as a Giant Tortoise's Lifespan.
In other words, 21.340 seconds is 0.00000000270 times the length of a Giant Tortoise's Lifespan, and the length of a Giant Tortoise's Lifespan is 370,000,000 times that amount.(for Adwaita, an Aldabra Giant Tortoise) (Dipsochelys dussumieri, formerly Geochelone gigantea)
Adwaita, an Aldabra Giant Tortoise who lived the later part of his life in the Alipore Zoological Gardens in Kolkata, India, was 7,900,000,000 seconds at the time of his death. Once a pet of Major-General Robert Clive, 1st Baron Clive, who is credited with securing India as a colony of Great Britain, Adwaita lived through the entirety of India's 6,000,000,000 seconds as a British colony.