18687891 has 16 divisors (see below), whose sum is σ = 26150400. Its totient is φ = 11848320.

The previous prime is 18687883. The next prime is 18687901. The reversal of 18687891 is 19878681.

It is not a de Polignac number, because 18687891 - 2³ = 18687883 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18687891.

It is not an unprimeable number, because it can be changed into a prime (18687821) 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, 13051 + ... + 14411.

It is an arithmetic number, because the mean of its divisors is an integer number (1634400).

Almost surely, 2^18687891 is an apocalyptic number.

18687891 is a deficient number, since it is larger than the sum of its proper divisors (7462509).

18687891 is a wasteful number, since it uses less digits than its factorization.

18687891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1586.

The product of its digits is 193536, while the sum is 48.

The square root of 18687891 is about 4322.9493404388. The cubic root of 18687891 is about 265.3709815367.

The spelling of 18687891 in words is "eighteen million, six hundred eighty-seven thousand, eight hundred ninety-one".