18991844 has 6 divisors (see below), whose sum is σ = 33235734. Its totient is φ = 9495920.

The previous prime is 18991831. The next prime is 18991867. The reversal of 18991844 is 44819981.

It can be written as a sum of positive squares in only one way, i.e., 16711744 + 2280100 = 4088^2 + 1510^2 .

It is a junction number, because it is equal to n+sod(n) for n = 18991795 and 18991804.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 2373977 + ... + 2373984.

It is an arithmetic number, because the mean of its divisors is an integer number (5539289).

Almost surely, 2^18991844 is an apocalyptic number.

It is an amenable number.

18991844 is a deficient number, since it is larger than the sum of its proper divisors (14243890).

18991844 is a wasteful number, since it uses less digits than its factorization.

18991844 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4747965 (or 4747963 counting only the distinct ones).

The product of its digits is 82944, while the sum is 44.

The square root of 18991844 is about 4357.9632857563. The cubic root of 18991844 is about 266.8019778570.

The spelling of 18991844 in words is "eighteen million, nine hundred ninety-one thousand, eight hundred forty-four".