15561565 has 4 divisors (see below), whose sum is σ = 18673884. Its totient is φ = 12449248.

The previous prime is 15561563. The next prime is 15561599. The reversal of 15561565 is 56516551.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 5044516 + 10517049 = 2246^2 + 3243^2 .

It is a cyclic number.

It is not a de Polignac number, because 15561565 - 2¹ = 15561563 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 15561565.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15561563) 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, 1556152 + ... + 1556161.

It is an arithmetic number, because the mean of its divisors is an integer number (4668471).

Almost surely, 2^15561565 is an apocalyptic number.

It is an amenable number.

15561565 is a deficient number, since it is larger than the sum of its proper divisors (3112319).

15561565 is an equidigital number, since it uses as much as digits as its factorization.

15561565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3112318.

The product of its digits is 22500, while the sum is 34.

The square root of 15561565 is about 3944.8149513000. The cubic root of 15561565 is about 249.6612211229.

The spelling of 15561565 in words is "fifteen million, five hundred sixty-one thousand, five hundred sixty-five".