18987805 has 8 divisors (see below), whose sum is σ = 22912344. Its totient is φ = 15105600.

The previous prime is 18987803. The next prime is 18987853. The reversal of 18987805 is 50878981.

It can be written as a sum of positive squares in 4 ways, for example, as 4356 + 18983449 = 66^2 + 4357^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 18987805 - 2¹ = 18987803 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 (18987803) 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 7 ways as a sum of consecutive naturals, for example, 9586 + ... + 11395.

It is an arithmetic number, because the mean of its divisors is an integer number (2864043).

Almost surely, 2^18987805 is an apocalyptic number.

It is an amenable number.

18987805 is a deficient number, since it is larger than the sum of its proper divisors (3924539).

18987805 is a wasteful number, since it uses less digits than its factorization.

18987805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21167.

The product of its (nonzero) digits is 161280, while the sum is 46.

The square root of 18987805 is about 4357.4998565691. The cubic root of 18987805 is about 266.7830629026.

The spelling of 18987805 in words is "eighteen million, nine hundred eighty-seven thousand, eight hundred five".