689 = 12 + 3 + 45 + 6 + 7 × 89
689 = 9 + 8 × 76 + 5 + 4 + 3 × 21
689 = 0^4 − 1^8 + 2^6 − 3^9 + 4^7 + 5^5 + 6^1 + 7^0 + 8^2 + 9^3
689 = 8^2 + 25^2 = 17^2 + 20^2
689^2 = 111^2 + 680^2 = 400^2 + 561^2
689 divides 83^4 - 1.
Strobogrammatic number: the same upside down.
a(n) = n*(4*n+1), n = 13
Semiprime (Product of 2 Primes)
Factors: 1, 13, 53, 689
Six hundred eighty-nine
Representations, Binary to Hexadecimal:
1010110001_2
221112_3
22301_4
10224_5
3105_6
2003_7
1261_8
845_9
577_11
495_12
410_13
373_14
30e_15
2b1_16
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