1111212121 has 2 divisors, whose sum is σ = 1111212122. Its totient is φ = 1111212120.

The previous prime is 1111212119. The next prime is 1111212203. The reversal of 1111212121 is 1212121111.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1030410000 + 80802121 = 32100^2 + 8989^2 .

It is a cyclic number.

It is not a de Polignac number, because 1111212121 - 2¹ = 1111212119 is a prime.

Together with 1111212119, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (1111212521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 555606060 + 555606061.

It is an arithmetic number, because the mean of its divisors is an integer number (555606061).

Almost surely, 2^1111212121 is an apocalyptic number.

It is an amenable number.

1111212121 is a deficient number, since it is larger than the sum of its proper divisors (1).

1111212121 is an equidigital number, since it uses as much as digits as its factorization.

1111212121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8, while the sum is 13.

The square root of 1111212121 is about 33334.8484472331. The cubic root of 1111212121 is about 1035.7755538213.

Adding to 1111212121 its reverse (1212121111), we get a palindrome (2323333232).

It can be divided in two parts, 111 and 1212121, that multiplied together give a palindrome (134545431).

The spelling of 1111212121 in words is "one billion, one hundred eleven million, two hundred twelve thousand, one hundred twenty-one".