1980
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Number
$1980$ (one thousand, nine hundred and eighty) is:
- $2^2 \times 3^2 \times 5 \times 11$
- The smallest term of the amicable triplet $\tuple {1980, 2016, 2556}$:
- $\map {\sigma_1} {1980} = \map {\sigma_1} {2016} = \map {\sigma_1} {2556} = 6552 = 1980 + 2016 + 2556$
- The $2$nd integer after $954$ whose digits are unchanged when subtracting its reversal:
- $1980 - 0891 = 1089$
Also see
Sources
- 1978: Thomas A. Whitelaw: An Introduction to Abstract Algebra ... (previous) ... (next): $\S 13$: The fundamental theorem of arithmetic
- 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $1980$
- 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $1980$