18861987 has 4 divisors (see below), whose sum is σ = 25149320. Its totient is φ = 12574656.

The previous prime is 18861967. The next prime is 18861989. The reversal of 18861987 is 78916881.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 78916881 = 3 ⋅26305627.

It is not a de Polignac number, because 18861987 - 2²² = 14667683 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18861989) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3143662 + ... + 3143667.

It is an arithmetic number, because the mean of its divisors is an integer number (6287330).

Almost surely, 2^18861987 is an apocalyptic number.

18861987 is a deficient number, since it is larger than the sum of its proper divisors (6287333).

18861987 is an equidigital number, since it uses as much as digits as its factorization.

18861987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6287332.

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

The square root of 18861987 is about 4343.0389130193. The cubic root of 18861987 is about 266.1924992096.

The spelling of 18861987 in words is "eighteen million, eight hundred sixty-one thousand, nine hundred eighty-seven".