18912491 has 4 divisors (see below), whose sum is σ = 20367312. Its totient is φ = 17457672.

The previous prime is 18912473. The next prime is 18912497. The reversal of 18912491 is 19421981.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18912491 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18912497) 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, 727391 + ... + 727416.

It is an arithmetic number, because the mean of its divisors is an integer number (5091828).

Almost surely, 2^18912491 is an apocalyptic number.

18912491 is a deficient number, since it is larger than the sum of its proper divisors (1454821).

18912491 is a wasteful number, since it uses less digits than its factorization.

18912491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1454820.

The product of its digits is 5184, while the sum is 35.

The square root of 18912491 is about 4348.8493880566. The cubic root of 18912491 is about 266.4298691285.

The spelling of 18912491 in words is "eighteen million, nine hundred twelve thousand, four hundred ninety-one".