8131561 has 4 divisors (see below), whose sum is σ = 8167300. Its totient is φ = 8095824.

The previous prime is 8131553. The next prime is 8131567. The reversal of 8131561 is 1651318.

8131561 is digitally balanced in base 3, 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.

It can be written as a sum of positive squares in 2 ways, for example, as 4305625 + 3825936 = 2075^2 + 1956^2 .

It is a cyclic number.

It is not a de Polignac number, because 8131561 - 2³ = 8131553 is a prime.

It is a super-2 number, since 2×8131561² = 132244568593442, which contains 22 as substring.

It is a Duffinian number.

8131561 is a lucky number.

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (8131567) 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, 17526 + ... + 17983.

It is an arithmetic number, because the mean of its divisors is an integer number (2041825).

Almost surely, 2^8131561 is an apocalyptic number.

It is an amenable number.

8131561 is a deficient number, since it is larger than the sum of its proper divisors (35739).

8131561 is a wasteful number, since it uses less digits than its factorization.

8131561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35738.

The product of its digits is 720, while the sum is 25.

The square root of 8131561 is about 2851.5892060393. The cubic root of 8131561 is about 201.0903861535.

Adding to 8131561 its reverse (1651318), we get a palindrome (9782879).

The spelling of 8131561 in words is "eight million, one hundred thirty-one thousand, five hundred sixty-one".