1991 = 12 × 34 × 56 + 78 + 9
1991 = 9 × 8 + 7 × 6 + 54 × 3 + 2 × 1
1991 = 0^7 + 1^8 + 2^9 − 3^6 + 4^5 + 5^4 + 6^2 + 7^0 + 8^3 + 9^1
1991 divides 42^5 - 1.
1991 cannot be written as a sum of 3 squares. (Integers that are not a sum of three squares)
Semiprime (Product of 2 Primes)
Factors: 1, 11, 181, 1991
One thousand, nine hundred ninety-one
Representations, Binary to Hexadecimal:
11111000111_2
2201202_3
133013_4
30431_5
13115_6
5543_7
3707_8
2652_9
1550_11
119b_12
ba2_13
a23_14
8cb_15
7c7_16
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Undergraduate Texts in Mathematics
Graduate Studies in Mathematics
