12665561 has 4 divisors (see below), whose sum is σ = 13410612. Its totient is φ = 11920512.

The previous prime is 12665557. The next prime is 12665563. The reversal of 12665561 is 16556621.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16556621 = 433 ⋅38237.

It can be written as a sum of positive squares in 2 ways, for example, as 10758400 + 1907161 = 3280^2 + 1381^2 .

It is a cyclic number.

It is not a de Polignac number, because 12665561 - 2² = 12665557 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (12665563) 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, 372500 + ... + 372533.

It is an arithmetic number, because the mean of its divisors is an integer number (3352653).

Almost surely, 2^12665561 is an apocalyptic number.

It is an amenable number.

12665561 is a deficient number, since it is larger than the sum of its proper divisors (745051).

12665561 is an equidigital number, since it uses as much as digits as its factorization.

12665561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 745050.

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

The square root of 12665561 is about 3558.8707478637. The cubic root of 12665561 is about 233.0995724650.

The spelling of 12665561 in words is "twelve million, six hundred sixty-five thousand, five hundred sixty-one".