18987693891 has 8 divisors (see below), whose sum is σ = 25347690240. Its totient is φ = 12643080072.

The previous prime is 18987693887. The next prime is 18987693899. The reversal of 18987693891 is 19839678981.

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

It is not a de Polignac number, because 18987693891 - 2² = 18987693887 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18987693899) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3842751 + ... + 3847688.

It is an arithmetic number, because the mean of its divisors is an integer number (3168461280).

Almost surely, 2^18987693891 is an apocalyptic number.

18987693891 is a deficient number, since it is larger than the sum of its proper divisors (6359996349).

18987693891 is an equidigital number, since it uses as much as digits as its factorization.

18987693891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7691265.

The product of its digits is 47029248, while the sum is 69.

The spelling of 18987693891 in words is "eighteen billion, nine hundred eighty-seven million, six hundred ninety-three thousand, eight hundred ninety-one".