It's about 650,000 times as heavy as a Nail.
It's about 0.0000007 times as heavy as The Golden Gate Bridge.
In other words, 521 kilograms is 0.0000006470 times the weight of The Golden Gate Bridge, and the weight of The Golden Gate Bridge is 1,550,000 times that amount.(San Francisco, California and Marin County, California) (Post 1986 weight reduction; total weight of bridge, anchorage, and approaches)
Following the completion of the 1986 project to eliminate excess material, the total weight of the Golden Gate Bridge — including its anchorages and approaches — is 805,000,000 kilograms. The two main cables in the spanning the bridge are spun out of a total of 129,000 km (80,200 mi) of wire.
It's about 3,000,000 times as heavy as a Raindrop.
In other words, the weight of a Raindrop is 0.000000300 times 521 kilograms.(a.k.a. drop, a.k.a. droplet) (average)
The weight of a raindrop depends heavily on the type of weather, but averages about 0.0002 kilograms. The familiar teardrop shape of a raindrop is actually an optical illusion, caused by the reflection of the light and the motion of the drop.
It's about 0.00000009 times as heavy as The Great Pyramid of Giza.
In other words, 521 kilograms is 0.0000000880 times the weight of The Great Pyramid of Giza, and the weight of The Great Pyramid of Giza is 11,000,000 times that amount.(a.k.a. Pyramid of Khufu, a.k.a. Pyramid of Cheops) (Cairo, Egypt)
The Great Pyramid of Giza has an estimated mass of 5,900,000,000 kilograms. The 2,300,000 stones used in the construction of the pyramid weighed an average 2,300 kilograms and were quarried from distances of up to 805 km (500 mi) away.
It's about 20,000,000 times as heavy as a Grain of Rice.
In other words, 521 kilograms is 18,000,000 times the weight of a Grain of Rice, and the weight of a Grain of Rice is 0.0000000560 times that amount.(long grain; 14% moisture content)
A single long grain of rice weighs an average of 0.0000290 kilograms. A staple through most of human history, archaeological evidence indicates that the earliest rice cultivation was about 11,500 years ago.
It's about 100,000,000 times as heavy as a Grain of Sand.
In other words, 521 kilograms is 120,000,000 times the weight of a Grain of Sand, and the weight of a Grain of Sand is 0.00000000830 times that amount.(medium grain)
With tremendous variety in the size of grain and the component material, grains of sand weigh an average of 0.00000440 kilograms. In 2007, a team of seven in Myrtle Beach created the world's tallest sandcastle, which measured 15.10 m (49.55 ft) in height.
It's about 150,000,000 times as heavy as a Sesame Seed.
In other words, 521 kilograms is 143,000,000 times the weight of a Sesame Seed, and the weight of a Sesame Seed is 0.000000006990 times that amount.(Sesamum indicum)
A sesame seed weighs approximately 0.000003640 kilograms. The McDonald's Big Mac sandwich, which is well-known for its sesame seed top bun, accounts for the consumption of an estimated 2,009.32 kg of sesame seeds each day.