12729921 has 4 divisors (see below), whose sum is σ = 16973232. Its totient is φ = 8486612.

The previous prime is 12729919. The next prime is 12729947. The reversal of 12729921 is 12992721.

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.

It is a cyclic number.

It is not a de Polignac number, because 12729921 - 2¹ = 12729919 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (12729901) 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, 2121651 + ... + 2121656.

It is an arithmetic number, because the mean of its divisors is an integer number (4243308).

Almost surely, 2^12729921 is an apocalyptic number.

It is an amenable number.

12729921 is a deficient number, since it is larger than the sum of its proper divisors (4243311).

12729921 is an equidigital number, since it uses as much as digits as its factorization.

12729921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4243310.

The product of its digits is 4536, while the sum is 33.

The square root of 12729921 is about 3567.9014840659. The cubic root of 12729921 is about 233.4937370983.

The spelling of 12729921 in words is "twelve million, seven hundred twenty-nine thousand, nine hundred twenty-one".