12665239921 has 4 divisors (see below), whose sum is σ = 13410254052. Its totient is φ = 11920225792.

The previous prime is 12665239907. The next prime is 12665239927. The reversal of 12665239921 is 12993256621.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7615005696 + 5050234225 = 87264^2 + 71065^2 .

It is a cyclic number.

It is not a de Polignac number, because 12665239921 - 2¹³ = 12665231729 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (12665239927) 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, 372507040 + ... + 372507073.

It is an arithmetic number, because the mean of its divisors is an integer number (3352563513).

Almost surely, 2^12665239921 is an apocalyptic number.

It is an amenable number.

12665239921 is a deficient number, since it is larger than the sum of its proper divisors (745014131).

12665239921 is an equidigital number, since it uses as much as digits as its factorization.

12665239921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 745014130.

The product of its digits is 349920, while the sum is 46.

The spelling of 12665239921 in words is "twelve billion, six hundred sixty-five million, two hundred thirty-nine thousand, nine hundred twenty-one".