18560921681 has 4 divisors (see below), whose sum is σ = 18593542500. Its totient is φ = 18528300864.

The previous prime is 18560921641. The next prime is 18560921689. The reversal of 18560921681 is 18612906581.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3255273025 + 15305648656 = 57055^2 + 123716^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18560921681 is a prime.

It is a super-2 number, since 2×18560921681² (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 (18560921689) 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, 16309556 + ... + 16310693.

It is an arithmetic number, because the mean of its divisors is an integer number (4648385625).

Almost surely, 2^18560921681 is an apocalyptic number.

It is an amenable number.

18560921681 is a deficient number, since it is larger than the sum of its proper divisors (32620819).

18560921681 is an equidigital number, since it uses as much as digits as its factorization.

18560921681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32620818.

The product of its (nonzero) digits is 207360, while the sum is 47.

The spelling of 18560921681 in words is "eighteen billion, five hundred sixty million, nine hundred twenty-one thousand, six hundred eighty-one".