18891491 has 12 divisors (see below), whose sum is σ = 20418552. Its totient is φ = 17466624.

The previous prime is 18891473. The next prime is 18891527. The reversal of 18891491 is 19419881.

It is not a de Polignac number, because 18891491 - 2¹⁰ = 18890467 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18891401) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 14915 + ... + 16131.

It is an arithmetic number, because the mean of its divisors is an integer number (1701546).

Almost surely, 2^18891491 is an apocalyptic number.

18891491 is a deficient number, since it is larger than the sum of its proper divisors (1527061).

18891491 is a wasteful number, since it uses less digits than its factorization.

18891491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1298 (or 1279 counting only the distinct ones).

The product of its digits is 20736, while the sum is 41.

The square root of 18891491 is about 4346.4342857105. The cubic root of 18891491 is about 266.3312200506.

The spelling of 18891491 in words is "eighteen million, eight hundred ninety-one thousand, four hundred ninety-one".