1221111221 has 4 divisors (see below), whose sum is σ = 1332121344. Its totient is φ = 1110101100.

The previous prime is 1221111167. The next prime is 1221111253.

1221111221 is nontrivially palindromic in base 10.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1221111221 - 2²⁶ = 1154002357 is a prime.

It is a super-2 number, since 2×1221111221² = 2982225228104221682, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1221111196 and 1221111205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221111271) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 55505045 + ... + 55505066.

It is an arithmetic number, because the mean of its divisors is an integer number (333030336).

Almost surely, 2^1221111221 is an apocalyptic number.

1221111221 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1221111221 is a deficient number, since it is larger than the sum of its proper divisors (111010123).

1221111221 is a wasteful number, since it uses less digits than its factorization.

1221111221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 111010122.

The product of its digits is 16, while the sum is 14.

The square root of 1221111221 is about 34944.4018549467. The cubic root of 1221111221 is about 1068.8540504649.

It can be divided in two parts, 12211 and 11221, that added together give a palindrome (23432).

The spelling of 1221111221 in words is "one billion, two hundred twenty-one million, one hundred eleven thousand, two hundred twenty-one".