945
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Number
$945$ (nine hundred and forty-five) is:
- $3^3 \times 5 \times 7$
- The $1$st odd abundant number:
- $\map {\sigma_1} {945} - 945 = 975 > 945$
- The $14$th primitive abundant number after $20$, $70$, $88$, $104$, $272$, $304$, $368$, $464$, $550$, $572$, $650$, $748$, $836$:
- $1 + 3 + 5 + 7 + 9 + 15 + 21 + 27 + 35 + 45 + 63 + 105 + 135 + 189 + 315 = 975 > 945$
- The $19$th primitive semiperfect number after $6$, $20$, $28$, $88$, $104$, $272$, $304$, $350$, $368$, $464$, $490$, $496$, $550$, $572$, $650$, $748$, $770$, $910$:
- $945 = 1 + 5 + 7 + 9 + 15 + 21 + 35 + 45 + 63 + 105 + 135 + 189 + 315$
Arithmetic Functions on $945$
\(\ds \map {\sigma_0} { 945 }\) | \(=\) | \(\ds 16\) | $\sigma_0$ of $945$ | |||||||||||
\(\ds \map \phi { 945 }\) | \(=\) | \(\ds 432\) | $\phi$ of $945$ | |||||||||||
\(\ds \map {\sigma_1} { 945 }\) | \(=\) | \(\ds 1920\) | $\sigma_1$ of $945$ |
Also see
Sources
- 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $945$
- 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $945$