18886991 has 4 divisors (see below), whose sum is σ = 18897672. Its totient is φ = 18876312.

The previous prime is 18886963. The next prime is 18887009. The reversal of 18886991 is 19968881.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 19968881 = 67 ⋅298043.

It is a cyclic number.

It is not a de Polignac number, because 18886991 - 2⁶ = 18886927 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 (18886951) 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, 1985 + ... + 6458.

It is an arithmetic number, because the mean of its divisors is an integer number (4724418).

Almost surely, 2^18886991 is an apocalyptic number.

18886991 is a deficient number, since it is larger than the sum of its proper divisors (10681).

18886991 is an equidigital number, since it uses as much as digits as its factorization.

18886991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10680.

The product of its digits is 248832, while the sum is 50.

The square root of 18886991 is about 4345.9165891674. The cubic root of 18886991 is about 266.3100714523.

The spelling of 18886991 in words is "eighteen million, eight hundred eighty-six thousand, nine hundred ninety-one".