18919999 has 4 divisors (see below), whose sum is σ = 21622864. Its totient is φ = 16217136.

The previous prime is 18919981. The next prime is 18920003. The reversal of 18919999 is 99991981.

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-18919999 is a prime.

It is a Duffinian number.

18919999 is a modest number, since divided by 9999 gives 1891 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18919939) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1351422 + ... + 1351435.

It is an arithmetic number, because the mean of its divisors is an integer number (5405716).

Almost surely, 2^18919999 is an apocalyptic number.

18919999 is a deficient number, since it is larger than the sum of its proper divisors (2702865).

18919999 is an equidigital number, since it uses as much as digits as its factorization.

18919999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2702864.

The product of its digits is 472392, while the sum is 55.

The square root of 18919999 is about 4349.7125192362. The cubic root of 18919999 is about 266.4651208009.

The spelling of 18919999 in words is "eighteen million, nine hundred nineteen thousand, nine hundred ninety-nine".