8128
Small list of interesting 4-digit numbers:
1061 4-digit prime numbers (all)
1105 various sums of two squares
2520 1st highly composite number
4225 various sums of two squares
5525 various sums of two squares
5777 first of two 'Stern numbers'
5993 second of the Stern numbers
6174 Kaprekar's constant 4-digit
8125 various sums of two squares
8128 ⇐ only 4-digit perfect number
collected by
artmetic monoalgorithmic digital art
horn_torus real world ↔ complex numbers
mathematical universe
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