18687891993 has 4 divisors (see below), whose sum is σ = 24917189328. Its totient is φ = 12458594660.

The previous prime is 18687891983. The next prime is 18687892007. The reversal of 18687891993 is 39919878681.

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 18687891993 - 2⁸ = 18687891737 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18687891923) 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, 3114648663 + ... + 3114648668.

It is an arithmetic number, because the mean of its divisors is an integer number (6229297332).

Almost surely, 2^18687891993 is an apocalyptic number.

It is an amenable number.

18687891993 is a deficient number, since it is larger than the sum of its proper divisors (6229297335).

18687891993 is an equidigital number, since it uses as much as digits as its factorization.

18687891993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6229297334.

The product of its digits is 47029248, while the sum is 69.

The spelling of 18687891993 in words is "eighteen billion, six hundred eighty-seven million, eight hundred ninety-one thousand, nine hundred ninety-three".