1211111111 has 8 divisors (see below), whose sum is σ = 1384396320. Its totient is φ = 1037893248.

The previous prime is 1211111107. The next prime is 1211111117. The reversal of 1211111111 is 1111111121.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1211111111 - 2² = 1211111107 is a prime.

It is a Duffinian number.

1211111111 is a modest number, since divided by 111111 gives 1211 as remainder.

It is a junction number, because it is equal to n+sod(n) for n = 1211111092 and 1211111101.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1211111117) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 30635 + ... + 57971.

It is an arithmetic number, because the mean of its divisors is an integer number (173049540).

Almost surely, 2^1211111111 is an apocalyptic number.

1211111111 is a deficient number, since it is larger than the sum of its proper divisors (173285209).

1211111111 is an equidigital number, since it uses as much as digits as its factorization.

1211111111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33673.

The product of its digits is 2, while the sum is 11.

The square root of 1211111111 is about 34801.0216947721. The cubic root of 1211111111 is about 1065.9283084302.

Adding to 1211111111 its reverse (1111111121), we get a palindrome (2322222232).

It can be divided in two parts, 121 and 1111111, that multiplied together give a palindrome (134444431).

The spelling of 1211111111 in words is "one billion, two hundred eleven million, one hundred eleven thousand, one hundred eleven".