18819993 has 4 divisors (see below), whose sum is σ = 25093328. Its totient is φ = 12546660.

The previous prime is 18819991. The next prime is 18820031. The reversal of 18819993 is 39991881.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 39991881 = 3 ⋅13330627.

It is not a de Polignac number, because 18819993 - 2¹ = 18819991 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18819991) 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, 3136663 + ... + 3136668.

It is an arithmetic number, because the mean of its divisors is an integer number (6273332).

Almost surely, 2^18819993 is an apocalyptic number.

It is an amenable number.

18819993 is a deficient number, since it is larger than the sum of its proper divisors (6273335).

18819993 is an equidigital number, since it uses as much as digits as its factorization.

18819993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6273334.

The product of its digits is 139968, while the sum is 48.

The square root of 18819993 is about 4338.2015859109. The cubic root of 18819993 is about 265.9948036372.

The spelling of 18819993 in words is "eighteen million, eight hundred nineteen thousand, nine hundred ninety-three".