11857561 has 4 divisors (see below), whose sum is σ = 11864500. Its totient is φ = 11850624.

The previous prime is 11857543. The next prime is 11857589. The reversal of 11857561 is 16575811.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 16575811 = 7 ⋅2367973.

It can be written as a sum of positive squares in 2 ways, for example, as 4648336 + 7209225 = 2156^2 + 2685^2 .

It is a cyclic number.

It is not a de Polignac number, because 11857561 - 2⁵ = 11857529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (11857591) 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, 1105 + ... + 4993.

It is an arithmetic number, because the mean of its divisors is an integer number (2966125).

Almost surely, 2^11857561 is an apocalyptic number.

It is an amenable number.

11857561 is a deficient number, since it is larger than the sum of its proper divisors (6939).

11857561 is an equidigital number, since it uses as much as digits as its factorization.

11857561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6938.

The product of its digits is 8400, while the sum is 34.

The square root of 11857561 is about 3443.4809423024. The cubic root of 11857561 is about 228.0333964110.

The spelling of 11857561 in words is "eleven million, eight hundred fifty-seven thousand, five hundred sixty-one".