12131221021 has 4 divisors (see below), whose sum is σ = 12140575612. Its totient is φ = 12121866432.

The previous prime is 12131221019. The next prime is 12131221031. The reversal of 12131221021 is 12012213121.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12012213121 = 67 ⋅179286763.

It can be written as a sum of positive squares in 2 ways, for example, as 5815740121 + 6315480900 = 76261^2 + 79470^2 .

It is a cyclic number.

It is not a de Polignac number, because 12131221021 - 2¹ = 12131221019 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 12131220986 and 12131221004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (12131221031) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4675350 + ... + 4677943.

It is an arithmetic number, because the mean of its divisors is an integer number (3035143903).

Almost surely, 2^12131221021 is an apocalyptic number.

It is an amenable number.

12131221021 is a deficient number, since it is larger than the sum of its proper divisors (9354591).

12131221021 is an equidigital number, since it uses as much as digits as its factorization.

12131221021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9354590.

The product of its (nonzero) digits is 48, while the sum is 16.

Adding to 12131221021 its reverse (12012213121), we get a palindrome (24143434142).

The spelling of 12131221021 in words is "twelve billion, one hundred thirty-one million, two hundred twenty-one thousand, twenty-one".