245

Previous  ... Next

Number

$245$ (two hundred and forty-five) is:

$5 \times 7^2$

The $2$nd of the $9$th pair of consecutive integers which both have $6$ divisors:

$\map {\sigma_0} {244} = \map {\sigma_0} {245} = 6$

The $4$th of the $1$st quadruple of consecutive integers which all have an equal divisors:

$\map {\sigma_0} {242} = \map {\sigma_0} {243} = \map {\sigma_0} {244} = \map {\sigma_0} {245} = 6$

The largest odd positive integer that cannot be expressed as the sum of exactly $5$ non-zero square numbers all of which are coprime.

The $16$th positive integer $n$ after $0$, $1$, $5$, $25$, $29$, $41$, $49$, $61$, $65$, $85$, $89$, $101$, $125$, $145$, $149$ such that the Fibonacci number $F_n$ ends in $n$

Arithmetic Functions on $245$

\(\ds \map {\sigma_0} { 245 }\)

\(=\)

\(\ds 6\)

$\sigma_0$ of $245$

Also see

• Odd Numbers Not Expressible as Sum of 5 Distinct Non-Zero Coprime Squares

• Previous  ... Next: Sequence of Fibonacci Numbers ending in Index
• Previous  ... Next: Pairs of Consecutive Integers with 6 Divisors
• Previous  ... Next: Sequence of 4 Consecutive Integers with Equal Number of Divisors

Sources

• 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $242$
• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $157$
• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $242$