12656561 has 2 divisors, whose sum is σ = 12656562. Its totient is φ = 12656560.

The previous prime is 12656549. The next prime is 12656563. The reversal of 12656561 is 16565621.

12656561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 8814961 + 3841600 = 2969^2 + 1960^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-12656561 is a prime.

Together with 12656563, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (12656563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6328280 + 6328281.

It is an arithmetic number, because the mean of its divisors is an integer number (6328281).

Almost surely, 2^12656561 is an apocalyptic number.

It is an amenable number.

12656561 is a deficient number, since it is larger than the sum of its proper divisors (1).

12656561 is an equidigital number, since it uses as much as digits as its factorization.

12656561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10800, while the sum is 32.

The square root of 12656561 is about 3557.6060771255. The cubic root of 12656561 is about 233.0443467690.

It can be divided in two parts, 1 and 2656561, that added together give a palindrome (2656562).

The spelling of 12656561 in words is "twelve million, six hundred fifty-six thousand, five hundred sixty-one".