85 (number)

85 ( eighty-five ) is a natural number located between the numbers 84 and 86.

In Math

85 is an odd two-digit number .
The number 85 is a semisimple number ^[1] .
85 is the decagonal number ^[2] .
85 is an octahedral number ^[2] .
85 is a centered triangular, centered square, centered 14-angled, and centered 28-angled number ^[2] .
85 is the maximum n for which the equation $1^{2}+2^{2}+3^{2}+...+n^{2}=1+2+3+...+m$ ${\ displaystyle 1 ^ {2} + 2 ^ {2} + 3 ^ {2} + ... + n ^ {2} = 1 + 2 + 3 + ... + m}$ $1^{2}+2^{2}+3^{2}+...+n^{2}=1+2+3+...+m$ has a solution ^[3] .
The number 85 is the Smith number ^[4] .
85 can be written as the sum of the exact squares of two numbers in two ways ^[5] : $85=2^{2}+9^{2}=6^{2}+7^{2}$ ${\ displaystyle 85 = 2 ^ {2} + 9 ^ {2} = 6 ^ {2} + 7 ^ {2}}$ $85=2^{2}+9^{2}=6^{2}+7^{2}$ .
Jacobstal number .
Evil number .