11

11 is a Prime Number, Prime(5)

11 = 1 + 23 + 4 + 5 + 67 − 89

11 = 9 + 8 − 7 + 65 − 43 − 21

11 = 0^6 − 1^7 + 2^9 − 3^8 + 4^2 + 5^5 + 6^1 + 7^4 + 8^3 + 9^0

11 = 1^2 + 1^2 + 3^2

Strobogrammatic number: the same upside down.

Sexy Prime (Primes p such that p + 6 is also prime)

11 = 11
= 22/2
= 33/3
= 44/4 = (4!×√4 − 4)÷ 4 = √4 × (4! − √4) ÷ 4
= 55/5
= 66/6
= 77/7
= 88/8
= 99/9

For every integer n, n^11 - n is divisible by 11

Number that is the sum of 11 positive 8th powers.

Number of fractions in Farey series of order 5: 0/1, 1/5, 1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5, 1/1

Number of Partitions of 6

Prime quadruple: numbers k such that k, k+2, k+6, k+8 are all prime.

Sophie Germain prime p (List): 2p+1 is also prime (23)

Prime of the form 2*n^2 + 11.

Prime p such that (p-1)/2 and (p-3)/4 are also prime.

Jacobsthal number: a(n) = a(n-1) + 2*a(n-2), with a(0) = 0, a(1) = 1; also a(n) = nearest integer to 2^n/3. n = 5

Heegner number d, (the ring of algebraic integers of \( \mathbb {Q} \left[{\sqrt {-d}}\right] \) has unique factorization)

Factors: 1, 11

Eleven

Representations, Binary to Hexadecimal:

Roman : XI

1011_2
102_3
23_4
21_5
15_6
14_7
13_8
12_9
10_11
b_12
b_13
b_14
b_15
b_16

10 <--- ---> 12