1231221221 has 4 divisors (see below), whose sum is σ = 1233270444. Its totient is φ = 1229172000.

The previous prime is 1231221191. The next prime is 1231221239. The reversal of 1231221221 is 1221221321.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1221221321 = 197 ⋅6199093.

It can be written as a sum of positive squares in 2 ways, for example, as 1157020225 + 74200996 = 34015^2 + 8614^2 .

It is a cyclic number.

It is not a de Polignac number, because 1231221221 - 2¹⁴ = 1231204837 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 1231221221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1231221421) 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, 1023710 + ... + 1024911.

It is an arithmetic number, because the mean of its divisors is an integer number (308317611).

Almost surely, 2^1231221221 is an apocalyptic number.

It is an amenable number.

1231221221 is a deficient number, since it is larger than the sum of its proper divisors (2049223).

1231221221 is an equidigital number, since it uses as much as digits as its factorization.

1231221221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2049222.

The product of its digits is 96, while the sum is 17.

The square root of 1231221221 is about 35088.7620328788. The cubic root of 1231221221 is about 1071.7957503886.

Adding to 1231221221 its reverse (1221221321), we get a palindrome (2452442542).

It can be divided in two parts, 12312 and 21221, that added together give a palindrome (33533).

The spelling of 1231221221 in words is "one billion, two hundred thirty-one million, two hundred twenty-one thousand, two hundred twenty-one".