265
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Number
$265$ (two hundred and sixty-five) is:
- $5 \times 53$
- The $6$th subfactorial after $0$, $1$, $2$, $9$, $44$:
- $265 = \, !6 = 6! \paren {1 - \dfrac 1 {1!} + \dfrac 1 {2!} - \dfrac 1 {3!} + \dfrac 1 {4!} - \dfrac 1 {5!} + \dfrac 1 {6!} }$
- The $10$th Smith number after $4$, $22$, $27$, $58$, $85$, $94$, $121$, $166$, $202$:
- $2 + 6 + 5 = 5 + 5 + 3 = 13$
- The $14$th number after $1$, $3$, $22$, $66$, $70$, $81$, $94$, $115$, $119$, $170$, $210$, $214$, $217$ whose divisor sum is square:
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- $\map {\sigma_1} {265} = 324 = 18^2$
- The $14$th positive integer after $50$, $65$, $85$, $125$, $130$, $145$, $170$, $185$, $200$, $205$, $221$, $250$, $260$ which can be expressed as the sum of two square numbers in two or more different ways:
- $265 = 16^2 + 3^2 = 12^2 + 11^2$
- The $17$th positive integer $n$ after $0$, $1$, $5$, $25$, $29$, $41$, $49$, $61$, $65$, $85$, $89$, $101$, $125$, $145$, $149$, $245$ such that the Fibonacci number $F_n$ ends in $n$
Also see
- Previous ... Next: Subfactorial
- Previous ... Next: Smith Number
- Previous ... Next: Numbers whose Divisor Sum is Square
- Previous ... Next: Sequence of Fibonacci Numbers ending in Index
Sources
- 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $265$
- 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $265$