20,615,673

Number
$20 \, 615 \, 673$ is:


 * $3 \times 13 \times 331 \times 1597$


 * The $2$nd known positive integer whose fourth power can be expressed as the sum of $3$ fourth powers, thus refuting Euler's Quartic Conjecture:
 * $20 \, 615 \, 673^4 = 2 \, 682 \, 440^4 + 15 \, 365 \, 639^4 + 18 \, 796 \, 760^4$