12165534721 has 4 divisors (see below), whose sum is σ = 12174232000. Its totient is φ = 12156837444.

The previous prime is 12165534683. The next prime is 12165534763. The reversal of 12165534721 is 12743556121.

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: 12743556121 = 63391 ⋅201031.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-12165534721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (12165534421) 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, 4346541 + ... + 4349338.

It is an arithmetic number, because the mean of its divisors is an integer number (3043558000).

Almost surely, 2^12165534721 is an apocalyptic number.

It is an amenable number.

12165534721 is a deficient number, since it is larger than the sum of its proper divisors (8697279).

12165534721 is an equidigital number, since it uses as much as digits as its factorization.

12165534721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8697278.

The product of its digits is 50400, while the sum is 37.

The spelling of 12165534721 in words is "twelve billion, one hundred sixty-five million, five hundred thirty-four thousand, seven hundred twenty-one".