1921 = 1 + 2 × 3 × 4 × (56 + 7 + 8 + 9)
1921 = (9 + 8 + 7 × 65) × 4 + 32 + 1
1921 = 0^6 + 1^8 + 2^9 − 3^7 + 4^5 + 5^3 + 6^2 + 7^4 + 8^1 + 9^0
1921 = 20^2 + 39^2 = 25^2 + 36^2
1921 = 5^4 + 6^4
1921^2 = 671^2 + 1800^2 = 1121^2 + 1560^2
1921 divides 98^4 - 1.
Pentanacci numbers: a(n) = a(n-1) + a(n-2) + a(n-3) + a(n-4) + a(n-5) with a(0) = a(1) = a(2) = a(3) = a(4) = 1. n = 14
a(n) = 2*n^2 - 1, n = 31
Semiprime (Product of 2 Primes)
Factors: 1, 17, 113, 1921
One thousand, nine hundred twenty-one
Representations, Binary to Hexadecimal:
11110000001_2
2122011_3
132001_4
30141_5
12521_6
5413_7
3601_8
2564_9
1497_11
1141_12
b4a_13
9b3_14
881_15
781_16
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Undergraduate Texts in Mathematics
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