12218561 has 4 divisors (see below), whose sum is σ = 12226500. Its totient is φ = 12210624.

The previous prime is 12218537. The next prime is 12218587. The reversal of 12218561 is 16581221.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 7728400 + 4490161 = 2780^2 + 2119^2 .

It is a cyclic number.

It is not a de Polignac number, because 12218561 - 2¹⁰ = 12217537 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 12218561.

It is not an unprimeable number, because it can be changed into a prime (12218761) 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, 836 + ... + 5013.

It is an arithmetic number, because the mean of its divisors is an integer number (3056625).

Almost surely, 2^12218561 is an apocalyptic number.

It is an amenable number.

12218561 is a deficient number, since it is larger than the sum of its proper divisors (7939).

12218561 is an equidigital number, since it uses as much as digits as its factorization.

12218561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7938.

The product of its digits is 960, while the sum is 26.

The square root of 12218561 is about 3495.5058289180. The cubic root of 12218561 is about 230.3244381624.

Adding to 12218561 its reverse (16581221), we get a palindrome (28799782).

The spelling of 12218561 in words is "twelve million, two hundred eighteen thousand, five hundred sixty-one".