8731561 has 4 divisors (see below), whose sum is σ = 8757072. Its totient is φ = 8706052.

The previous prime is 8731531. The next prime is 8731571. The reversal of 8731561 is 1651378.

8731561 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: 1651378 = 2 ⋅825689.

It is a cyclic number.

It is not a de Polignac number, because 8731561 - 2⁵ = 8731529 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (8731501) 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, 12235 + ... + 12928.

It is an arithmetic number, because the mean of its divisors is an integer number (2189268).

Almost surely, 2^8731561 is an apocalyptic number.

It is an amenable number.

8731561 is a deficient number, since it is larger than the sum of its proper divisors (25511).

8731561 is a wasteful number, since it uses less digits than its factorization.

8731561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25510.

The product of its digits is 5040, while the sum is 31.

The square root of 8731561 is about 2954.9214879587. The cubic root of 8731561 is about 205.9194158053.

The spelling of 8731561 in words is "eight million, seven hundred thirty-one thousand, five hundred sixty-one".