18939293781 has 4 divisors (see below), whose sum is σ = 25252391712. Its totient is φ = 12626195852.

The previous prime is 18939293777. The next prime is 18939293831. The reversal of 18939293781 is 18739293981.

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: 18739293981 = 3 ⋅6246431327.

It is a cyclic number.

It is not a de Polignac number, because 18939293781 - 2² = 18939293777 is a prime.

It is a super-2 number, since 2×18939293781² (a number of 21 digits) contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18939293701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3156548961 + ... + 3156548966.

It is an arithmetic number, because the mean of its divisors is an integer number (6313097928).

Almost surely, 2^18939293781 is an apocalyptic number.

It is an amenable number.

18939293781 is a deficient number, since it is larger than the sum of its proper divisors (6313097931).

18939293781 is an equidigital number, since it uses as much as digits as its factorization.

18939293781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6313097930.

The product of its digits is 5878656, while the sum is 60.

The spelling of 18939293781 in words is "eighteen billion, nine hundred thirty-nine million, two hundred ninety-three thousand, seven hundred eighty-one".