12643561 has 4 divisors (see below), whose sum is σ = 14449792. Its totient is φ = 10837332.

The previous prime is 12643549. The next prime is 12643571. The reversal of 12643561 is 16534621.

12643561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 an emirpimes, since its reverse is a distinct semiprime: 16534621 = 79 ⋅209299.

It is a cyclic number.

It is not a de Polignac number, because 12643561 - 2⁹ = 12643049 is a prime.

It is not an unprimeable number, because it can be changed into a prime (12643511) 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, 903105 + ... + 903118.

It is an arithmetic number, because the mean of its divisors is an integer number (3612448).

Almost surely, 2^12643561 is an apocalyptic number.

It is an amenable number.

12643561 is a deficient number, since it is larger than the sum of its proper divisors (1806231).

12643561 is an equidigital number, since it uses as much as digits as its factorization.

12643561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1806230.

The product of its digits is 4320, while the sum is 28.

The square root of 12643561 is about 3555.7785364108. The cubic root of 12643561 is about 232.9645300805.

The spelling of 12643561 in words is "twelve million, six hundred forty-three thousand, five hundred sixty-one".