18621891 has 12 divisors (see below), whose sum is σ = 26937768. Its totient is φ = 12396384.

The previous prime is 18621877. The next prime is 18621899. The reversal of 18621891 is 19812681.

It is not a de Polignac number, because 18621891 - 2¹⁴ = 18605507 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18621899) 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 11 ways as a sum of consecutive naturals, for example, 8296 + ... + 10298.

It is an arithmetic number, because the mean of its divisors is an integer number (2244814).

Almost surely, 2^18621891 is an apocalyptic number.

18621891 is a deficient number, since it is larger than the sum of its proper divisors (8315877).

18621891 is a wasteful number, since it uses less digits than its factorization.

18621891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3042 (or 3039 counting only the distinct ones).

The product of its digits is 6912, while the sum is 36.

The square root of 18621891 is about 4315.3089113064. The cubic root of 18621891 is about 265.0582095933.

The spelling of 18621891 in words is "eighteen million, six hundred twenty-one thousand, eight hundred ninety-one".