187

Previous  ... Next

Number

$187$ (one hundred and eighty-seven) is:

$11 \times 17$

The $1$st of the $3$-digit integers $m$ which need the largest number of reverse-and-add process iterations ($23$) before reaching a palindromic number:

$187$, $968$, $1837$, $\ldots$, $8713200023178$

The $7$th positive integer after $1$, $7$, $102$, $110$, $142$, $159$ the sum of whose divisors is a cube:

$\map {\sigma_1} {187} = 216 = 6^3$

The $11$th second pentagonal number after $2$, $7$, $15$, $26$, $40$, $57$, $77$, $100$, $126$, $155$:

$187 = \dfrac {11 \paren {3 \times 11 + 1} } 2$

The $22$nd generalized pentagonal number after $1$, $2$, $5$, $7$, $12$, $15$, $22$, $26$, $35$, $40$, $51$, $57$, $70$, $77$, $92$, $100$, $117$, $126$, $145$, $155$, $176$:

$187 = \dfrac {11 \paren {3 \times 11 + 1} } 2$

Also see

• Previous  ... Next: Second Pentagonal Number
• Previous  ... Next: Integers whose Divisor Sum is Cube
• Previous  ... Next: Generalized Pentagonal Number
• Next: 3-Digit Numbers forming Longest Reverse-and-Add Sequence

Sources

• 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $187$
• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $187$