It is a happy number.
1111111111 is nontrivially palindromic in base 10.
It is a cyclic number.
It is a de Polignac number, because none of the positive numbers 2k-1111111111 is a prime.
1111111111 is a strobogrammatic number because it is the same when read upside-down.
It is a deceptive number, since it divides R1111111110.
It is a Duffinian number.
1111111111 is a nontrivial repdigit in base 10.
It is a plaindrome in base 10.
It is a nialpdrome in base 10.
It is a zygodrome in base 10.
It is a congruent number.
It is a Kaprekar number, because its square (1234567900987654321) can be partitioned into two parts whose sum is 1111111111.
Almost surely, 21111111111 is an apocalyptic number.
1111111111 is a gapful number since it is divisible by the number (11) formed by its first and last digit.
1111111111 is a wasteful number, since it uses less digits than its factorization.
1111111111 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 9414.
The square root of 1111111111 is about 33333.3333316667. Note that the first 5 decimals coincide. The cubic root of 1111111111 is about 1035.7441686168.
The spelling of 1111111111 in words is "one billion, one hundred eleven million, one hundred eleven thousand, one hundred eleven".