18685351681 has 4 divisors (see below), whose sum is σ = 18921875200. Its totient is φ = 18448828164.

The previous prime is 18685351679. The next prime is 18685351693. The reversal of 18685351681 is 18615358681.

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 18685351681 - 2¹ = 18685351679 is a prime.

It is a super-2 number, since 2×18685351681² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18685351651) 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, 118261641 + ... + 118261798.

It is an arithmetic number, because the mean of its divisors is an integer number (4730468800).

Almost surely, 2^18685351681 is an apocalyptic number.

It is an amenable number.

18685351681 is a deficient number, since it is larger than the sum of its proper divisors (236523519).

18685351681 is an equidigital number, since it uses as much as digits as its factorization.

18685351681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 236523518.

The product of its digits is 1382400, while the sum is 52.

The spelling of 18685351681 in words is "eighteen billion, six hundred eighty-five million, three hundred fifty-one thousand, six hundred eighty-one".