18919121 has 4 divisors (see below), whose sum is σ = 20374452. Its totient is φ = 17463792.

The previous prime is 18919111. The next prime is 18919127. The reversal of 18919121 is 12191981.

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

It can be written as a sum of positive squares in 2 ways, for example, as 3748096 + 15171025 = 1936^2 + 3895^2 .

It is a cyclic number.

It is not a de Polignac number, because 18919121 - 2⁶ = 18919057 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18919127) 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, 727646 + ... + 727671.

It is an arithmetic number, because the mean of its divisors is an integer number (5093613).

Almost surely, 2^18919121 is an apocalyptic number.

It is an amenable number.

18919121 is a deficient number, since it is larger than the sum of its proper divisors (1455331).

18919121 is a wasteful number, since it uses less digits than its factorization.

18919121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1455330.

The product of its digits is 1296, while the sum is 32.

The square root of 18919121 is about 4349.6115918551. The cubic root of 18919121 is about 266.4609988839.

The spelling of 18919121 in words is "eighteen million, nine hundred nineteen thousand, one hundred twenty-one".