18506891 has 4 divisors (see below), whose sum is σ = 19930512. Its totient is φ = 17083272.

The previous prime is 18506869. The next prime is 18506903. The reversal of 18506891 is 19860581.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19860581 = 13 ⋅1527737.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18506891 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18506291) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 711791 + ... + 711816.

It is an arithmetic number, because the mean of its divisors is an integer number (4982628).

Almost surely, 2^18506891 is an apocalyptic number.

18506891 is a deficient number, since it is larger than the sum of its proper divisors (1423621).

18506891 is a wasteful number, since it uses less digits than its factorization.

18506891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1423620.

The product of its (nonzero) digits is 17280, while the sum is 38.

The square root of 18506891 is about 4301.9636214175. The cubic root of 18506891 is about 264.5114577960.

The spelling of 18506891 in words is "eighteen million, five hundred six thousand, eight hundred ninety-one".