36

Number
$36$ (thirty-six) is:


 * $2^2 \times 3^2$


 * The $6$th square number after $1, 4, 9, 16, 25$:
 * $36 = 6 \times 6$


 * The $8$th triangular number after $1, 3, 6, 10, 15, 21, 28$:
 * $36 = 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 = \dfrac {8 \times \left({8 + 1}\right)} 2$


 * The $7$th superabundant number after $1, 2, 4, 6, 12, 24$:
 * $\dfrac {\sigma \left({36}\right)} {36} = \dfrac {91} {36} = 2 \cdotp 52 \dot 7$


 * The $8$th semiperfect number after $6, 12, 18, 20, 24, 28, 30$:
 * $36 = 3 + 6 + 9 + 18$


 * The $13$th Ulam number after $1, 2, 3, 4, 6, 8, 11, 13, 16, 18, 26, 28$:
 * $36 = 8 + 28$