645 = 123 + 45 + 6 × 78 + 9
645 = (98 + 7) × 6 + 5 + 4 + 3 + 2 + 1
645 = 0^5 + 1^7 + 2^9 − 3^8 + 4^6 + 5^3 + 6^1 + 7^4 + 8^2 + 9^0
Number of edges in an equilateral triangle when n internal equilateral triangles are drawn between the 3n points that divide each side into n+1 equal parts. (n=11)
Sphenic number: Product of 3 distinct Primes, (List)
Factors: 1, 3, 5, 15, 43, 129, 215, 645
Representations, Binary to Hexadecimal:
1010000101_2
212220_3
22011_4
10040_5
2553_6
1611_7
1205_8
786_9
537_11
459_12
3a8_13
341_14
2d0_15
285_16
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Undergraduate Texts in Mathematics
Graduate Studies in Mathematics
