1221313121 has 4 divisors (see below), whose sum is σ = 1395786432. Its totient is φ = 1046839812.

The previous prime is 1221313097. The next prime is 1221313139. The reversal of 1221313121 is 1213131221.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1213131221 = 6271 ⋅193451.

It is a cyclic number.

It is not a de Polignac number, because 1221313121 - 2²⁶ = 1154204257 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1221313121.

It is not an unprimeable number, because it can be changed into a prime (1221313021) 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, 87236645 + ... + 87236658.

It is an arithmetic number, because the mean of its divisors is an integer number (348946608).

Almost surely, 2^1221313121 is an apocalyptic number.

It is an amenable number.

1221313121 is a deficient number, since it is larger than the sum of its proper divisors (174473311).

1221313121 is an equidigital number, since it uses as much as digits as its factorization.

1221313121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 174473310.

The product of its digits is 72, while the sum is 17.

The square root of 1221313121 is about 34947.2906102891. The cubic root of 1221313121 is about 1068.9129557572.

Adding to 1221313121 its reverse (1213131221), we get a palindrome (2434444342).

It can be divided in two parts, 1 and 221313121, that added together give a palindrome (221313122).

The spelling of 1221313121 in words is "one billion, two hundred twenty-one million, three hundred thirteen thousand, one hundred twenty-one".