18939993 has 8 divisors (see below), whose sum is σ = 25373856. Its totient is φ = 12566400.

The previous prime is 18939983. The next prime is 18939997. The reversal of 18939993 is 39993981.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a de Polignac number, because none of the positive numbers 2^k-18939993 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18939997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14328 + ... + 15593.

It is an arithmetic number, because the mean of its divisors is an integer number (3171732).

Almost surely, 2^18939993 is an apocalyptic number.

It is an amenable number.

18939993 is a deficient number, since it is larger than the sum of its proper divisors (6433863).

18939993 is a wasteful number, since it uses less digits than its factorization.

18939993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30135.

The product of its digits is 472392, while the sum is 51.

The square root of 18939993 is about 4352.0102251718. The cubic root of 18939993 is about 266.5589514615.

The spelling of 18939993 in words is "eighteen million, nine hundred thirty-nine thousand, nine hundred ninety-three".