18881861 has 2 divisors, whose sum is σ = 18881862. Its totient is φ = 18881860.

The previous prime is 18881809. The next prime is 18881867. The reversal of 18881861 is 16818881.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15249025 + 3632836 = 3905^2 + 1906^2 .

It is a cyclic number.

It is not a de Polignac number, because 18881861 - 2¹⁸ = 18619717 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18881867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9440930 + 9440931.

It is an arithmetic number, because the mean of its divisors is an integer number (9440931).

Almost surely, 2^18881861 is an apocalyptic number.

It is an amenable number.

18881861 is a deficient number, since it is larger than the sum of its proper divisors (1).

18881861 is an equidigital number, since it uses as much as digits as its factorization.

18881861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 24576, while the sum is 41.

The square root of 18881861 is about 4345.3263398737. The cubic root of 18881861 is about 266.2859579522.

The spelling of 18881861 in words is "eighteen million, eight hundred eighty-one thousand, eight hundred sixty-one".