18871861 has 2 divisors, whose sum is σ = 18871862. Its totient is φ = 18871860.

The previous prime is 18871859. The next prime is 18871873. The reversal of 18871861 is 16817881.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13140625 + 5731236 = 3625^2 + 2394^2 .

It is an emirp because it is prime and its reverse (16817881) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18871861 - 2¹ = 18871859 is a prime.

It is a super-2 number, since 2×18871861² = 712294275206642, which contains 22 as substring.

Together with 18871859, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18871841) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9435930 + 9435931.

It is an arithmetic number, because the mean of its divisors is an integer number (9435931).

Almost surely, 2^18871861 is an apocalyptic number.

It is an amenable number.

18871861 is a deficient number, since it is larger than the sum of its proper divisors (1).

18871861 is an equidigital number, since it uses as much as digits as its factorization.

18871861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 21504, while the sum is 40.

The square root of 18871861 is about 4344.1755259197. The cubic root of 18871861 is about 266.2389405209.

The spelling of 18871861 in words is "eighteen million, eight hundred seventy-one thousand, eight hundred sixty-one".