12666221 has 4 divisors (see below), whose sum is σ = 12674112. Its totient is φ = 12658332.

The previous prime is 12666211. The next prime is 12666239. The reversal of 12666221 is 12266621.

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 a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 12266621 = 251 ⋅48871.

It is a cyclic number.

It is not a de Polignac number, because 12666221 - 2¹⁰ = 12665197 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (12666211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 581 + ... + 5066.

It is an arithmetic number, because the mean of its divisors is an integer number (3168528).

Almost surely, 2^12666221 is an apocalyptic number.

It is an amenable number.

12666221 is a deficient number, since it is larger than the sum of its proper divisors (7891).

12666221 is an equidigital number, since it uses as much as digits as its factorization.

12666221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7890.

The product of its digits is 1728, while the sum is 26.

The square root of 12666221 is about 3558.9634726982. The cubic root of 12666221 is about 233.1036213196.

The spelling of 12666221 in words is "twelve million, six hundred sixty-six thousand, two hundred twenty-one".