18857561 has 4 divisors (see below), whose sum is σ = 18909312. Its totient is φ = 18805812.

The previous prime is 18857533. The next prime is 18857591. The reversal of 18857561 is 16575881.

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: 16575881 = 7 ⋅2367983.

It is a cyclic number.

It is not a de Polignac number, because 18857561 - 2⁶ = 18857497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18857591) 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, 25325 + ... + 26058.

It is an arithmetic number, because the mean of its divisors is an integer number (4727328).

Almost surely, 2^18857561 is an apocalyptic number.

It is an amenable number.

18857561 is a deficient number, since it is larger than the sum of its proper divisors (51751).

18857561 is an equidigital number, since it uses as much as digits as its factorization.

18857561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51750.

The product of its digits is 67200, while the sum is 41.

The square root of 18857561 is about 4342.5293320829. The cubic root of 18857561 is about 266.1716767274.

The spelling of 18857561 in words is "eighteen million, eight hundred fifty-seven thousand, five hundred sixty-one".