It's about 100 times as heavy as a Cat.
In other words, the weight of a Cat is 0.01 times 521 kilograms.(Felis catus) (Domestic; healthy weight)
The average domestic cat should weigh between 4 and 5 kg. Cats are known for their righting reflex, which allows them to land on their feet and survive falls from heights of 1 m (3 ft) up to about 21 m.
It's about 200 times as heavy as a Brick.
In other words, 521 kilograms is 180 times the weight of a Brick, and the weight of a Brick is 0.0056 times that amount.(Standard, traditional face brick - 1,900 cu. cm (120 cu. in))
A standard, traditional face brick weighs an average of 2.9 kg. The steeple of the Church of St. Martin in Landshut, Germany is said to be the tallest brick tower in the world at a height of 130.6 m (428.5 ft) and was constructed using an estimated 650,000 bricks.
It's about 250 times as heavy as a Chihuahua.
In other words, 521 kilograms is 232 times the weight of a Chihuahua, and the weight of a Chihuahua is 0.00431 times that amount.(a.k.a. Chihuahue(o) (FCI standard)
The F&d&ration Cynologique Internationale (FCI) calls for Chihuahuas to weigh about 1.5 to 3 kg. Relative to their body sizes, Chihuahuas have the largest brain size of any dog breed.
It's about 400 times as heavy as a Human Brain.
In other words, 521 kilograms is 386 times the weight of a Human Brain, and the weight of a Human Brain is 0.00259 times that amount.(adult)
The average weight of an adult human brain is between 1.350 kilograms. In humans and primates, sight and vision utilize about 30 different parts of the brain which together account for about half of the brain's size.
It's about 500 times as heavy as a liter of Water.
In other words, 521 kilograms is 520.98540 times the weight of a liter of Water, and the weight of a liter of Water is 0.00191944 times that amount.(fresh; 4° C / 39.2° F; maximum density)
Contrary to popular belief, 1 liter (0.0.264172052358148 gal) of water at 4° C / 39.2° F (its point of maximum density) weighs 1.000028 kg rather than 1 kg exactly. The total volume of water on the planet Earth is about 13,590,000,000,000,000,000 (13.59 quntillion) L (3,590,000,000,000,000,000 gallons).
It's about 850 times as heavy as a Basketball.
In other words, 521 kilograms is 835.351553440 times the weight of a Basketball, and the weight of a Basketball is 0.0011971007846 times that amount.(NBA official ball standards, Size 7)
A regulation NBA basketball, manufactured by Spalding, is known as a Size 7 ball and weighs 0.623689508750 kilograms. These balls have 4,118 pebbles each with a diameter of 2.5 mm
It's about 1,000 times as heavy as a Football (Soccer).
In other words, 521 kilograms is 1,200 times the weight of a Football (Soccer), and the weight of a Football (Soccer) is 0.00083 times that amount.(a.k.a. Soccer, a.k.a. Association Football) (FIFA Law 2 specification)
According to FIFA's Law of the Game number 2, a football must weigh between 0.410 kilograms and 0.450 kilograms. An artifact on display at the Smith Art Gallery in Museum in Stirling, Scotland is said to be the world's oldest football and is about one-third to one-half the size of a modern football.