15566561 has 4 divisors (see below), whose sum is σ = 16243392. Its totient is φ = 14889732.

The previous prime is 15566549. The next prime is 15566563. The reversal of 15566561 is 16566551.

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.

It is a cyclic number.

It is not a de Polignac number, because 15566561 - 2¹⁸ = 15304417 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15566563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 338381 + ... + 338426.

It is an arithmetic number, because the mean of its divisors is an integer number (4060848).

Almost surely, 2^15566561 is an apocalyptic number.

It is an amenable number.

15566561 is a deficient number, since it is larger than the sum of its proper divisors (676831).

15566561 is an equidigital number, since it uses as much as digits as its factorization.

15566561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 676830.

The product of its digits is 27000, while the sum is 35.

The square root of 15566561 is about 3945.4481367774. The cubic root of 15566561 is about 249.6879359596.

The spelling of 15566561 in words is "fifteen million, five hundred sixty-six thousand, five hundred sixty-one".