1221111121 has 4 divisors (see below), whose sum is σ = 1222504372. Its totient is φ = 1219717872.

The previous prime is 1221111097. The next prime is 1221111167. The reversal of 1221111121 is 1211111221.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 981944896 + 239166225 = 31336^2 + 15465^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221111121 - 2¹³ = 1221102929 is a prime.

It is a super-2 number, since 2×1221111121² = 2982224739659753282, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1221114121) 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 in 3 ways as a sum of consecutive naturals, for example, 695310 + ... + 697063.

It is an arithmetic number, because the mean of its divisors is an integer number (305626093).

Almost surely, 2^1221111121 is an apocalyptic number.

It is an amenable number.

1221111121 is a deficient number, since it is larger than the sum of its proper divisors (1393251).

1221111121 is an equidigital number, since it uses as much as digits as its factorization.

1221111121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1393250.

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

The square root of 1221111121 is about 34944.4004241023. The cubic root of 1221111121 is about 1068.8540212878.

Adding to 1221111121 its reverse (1211111221), we get a palindrome (2432222342).

It can be divided in two parts, 12211 and 11121, that added together give a palindrome (23332).

The spelling of 1221111121 in words is "one billion, two hundred twenty-one million, one hundred eleven thousand, one hundred twenty-one".