1211221221 has 64 divisors (see below), whose sum is σ = 1974067200. Its totient is φ = 645926400.

The previous prime is 1211221213. The next prime is 1211221237. The reversal of 1211221221 is 1221221121.

It is not a de Polignac number, because 1211221221 - 2³ = 1211221213 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1211221221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1211261221) 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 63 ways as a sum of consecutive naturals, for example, 4469316 + ... + 4469586.

It is an arithmetic number, because the mean of its divisors is an integer number (30844800).

Almost surely, 2^1211221221 is an apocalyptic number.

It is an amenable number.

1211221221 is a deficient number, since it is larger than the sum of its proper divisors (762845979).

1211221221 is a wasteful number, since it uses less digits than its factorization.

1211221221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 530.

The product of its digits is 32, while the sum is 15.

The square root of 1211221221 is about 34802.6036526005. The cubic root of 1211221221 is about 1065.9606109466.

Adding to 1211221221 its reverse (1221221121), we get a palindrome (2432442342).

It can be divided in two parts, 12112 and 21221, that added together give a palindrome (33333).

The spelling of 1211221221 in words is "one billion, two hundred eleven million, two hundred twenty-one thousand, two hundred twenty-one".