18781861 has 16 divisors (see below), whose sum is σ = 22720000. Its totient is φ = 15167088.

The previous prime is 18781831. The next prime is 18781891. The reversal of 18781861 is 16818781.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (18781831) and next prime (18781891).

It is a cyclic number.

It is not a de Polignac number, because 18781861 - 2⁷ = 18781733 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18781801) 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 15 ways as a sum of consecutive naturals, for example, 37390 + ... + 37888.

It is an arithmetic number, because the mean of its divisors is an integer number (1420000).

Almost surely, 2^18781861 is an apocalyptic number.

It is an amenable number.

18781861 is a deficient number, since it is larger than the sum of its proper divisors (3938139).

18781861 is a wasteful number, since it uses less digits than its factorization.

18781861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 808.

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

The square root of 18781861 is about 4333.8044487494. The cubic root of 18781861 is about 265.8150343194.

The spelling of 18781861 in words is "eighteen million, seven hundred eighty-one thousand, eight hundred sixty-one".