18823561 has 4 divisors (see below), whose sum is σ = 19081492. Its totient is φ = 18565632.

The previous prime is 18823549. The next prime is 18823577. The reversal of 18823561 is 16532881.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16532881 = 41 ⋅403241.

It can be written as a sum of positive squares in 2 ways, for example, as 4648336 + 14175225 = 2156^2 + 3765^2 .

It is a cyclic number.

It is not a de Polignac number, because 18823561 - 2¹⁷ = 18692489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18823501) 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, 128856 + ... + 129001.

It is an arithmetic number, because the mean of its divisors is an integer number (4770373).

Almost surely, 2^18823561 is an apocalyptic number.

It is an amenable number.

18823561 is a deficient number, since it is larger than the sum of its proper divisors (257931).

18823561 is an equidigital number, since it uses as much as digits as its factorization.

18823561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 257930.

The product of its digits is 11520, while the sum is 34.

The square root of 18823561 is about 4338.6127967358. The cubic root of 18823561 is about 266.0116121714.

The spelling of 18823561 in words is "eighteen million, eight hundred twenty-three thousand, five hundred sixty-one".