18791993 has 4 divisors (see below), whose sum is σ = 20500368. Its totient is φ = 17083620.

The previous prime is 18791977. The next prime is 18791999. The reversal of 18791993 is 39919781.

It is a happy number.

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.

It is a cyclic number.

It is not a de Polignac number, because 18791993 - 2⁴ = 18791977 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18791999) 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, 854171 + ... + 854192.

It is an arithmetic number, because the mean of its divisors is an integer number (5125092).

Almost surely, 2^18791993 is an apocalyptic number.

It is an amenable number.

18791993 is a deficient number, since it is larger than the sum of its proper divisors (1708375).

18791993 is a wasteful number, since it uses less digits than its factorization.

18791993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1708374.

The product of its digits is 122472, while the sum is 47.

The square root of 18791993 is about 4334.9732409785. The cubic root of 18791993 is about 265.8628242904.

The spelling of 18791993 in words is "eighteen million, seven hundred ninety-one thousand, nine hundred ninety-three".