It's about as heavy as a Grizzly Bear
(a.k.a. brown bear, a.k.a. silver bear, Ursus arctos horribilis) (Adult, male, coastal area population average)
An adult, male grizzly bear from a coastal area (where food is plentiful) can weigh up to 521 kg. In spite of their tremendous size, grizzly bears can run at speeds of up to 55 kph (34 mph).
It's about one-and-one-tenth times as heavy as a Polar Bear
In other words, 521 kilograms is 1.01 times the weight of a Polar Bear, and the weight of a Polar Bear is 0.990 times that amount.(Ursus maritimus) (adult, male)
An adult, male polar bear weighs between 352 and 680 kg. Polar bears are so heavily insulated by their 9.9 cm (3.9 in) layer of blubber that they are often difficult to detect using infrared photography sensors.
It's about one-and-one-fifth times as heavy as a Grand Piano
It's about one-and-one-fifth times as heavy as a Horse
In other words, the weight of a Horse is 0.830 times 521 kilograms.(Equus ferus caballus) (Arabian, adult)
n Arabian riding horse (or similar breed) weighs between 380 and 450 kg. During races, horses must carry jockeys and their equipment, which in the Kentucky Derby, for example, can weigh up to 54.4 kg.
It's about three-fourths as heavy as a Cow
In other words, the weight of a Cow is 1.30 times 521 kilograms.(for Holstein, a.k.a. Holstein Friesian, a.k.a. Friesian, Bos primigenius) (adult, heifer)
A mature Holstein cow (the well-known black-and-white, spotted breed of cow) typically weighs 680 kg. President William Howard Taft (1909 - 1913) kept a Holstein cow named Pauline Wayne on the White House grounds — a gift from a Wisconsin senator and the source of the First Family's milk.
It's about two times as heavy as a Pig
In other words, 521 kilograms is 2.10 times the weight of a Pig, and the weight of a Pig is 0.480 times that amount.(Domestic pig, Sus scrofa domesticus, a.k.a. S. domesticus) (adult)
Domestic pigs weigh between 50 kg and 450 kg. The titular character "Babe the pig" in the 1995 family film was played by 48 different American Yorkshire piglets due to the length of filming and the rate at which piglets reach adulthood.
It's about two-and-a-half times as heavy as a cubic meter of Snow
In other words, the weight of a cubic meter of Snow is 0.430 times 521 kilograms.(Freshly fallen, standard conditions; measurements taken in Norway, 1965-68)
One cubic meter of freshly fallen snow under standard conditions weighs an average of 230 kg. Assembled in 2008, the world record largest snowman was constructed of 5,900,000 kg of snow and stood 37.21 m (122.1 ft) tall.