18281473681 has 3 divisors (see below), whose sum is σ = 18281608891. Its totient is φ = 18281338472.

The previous prime is 18281473669. The next prime is 18281473699. The reversal of 18281473681 is 18637418281.

The square root of 18281473681 is 135209.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 5782233681 + 12499240000 = 76041^2 + 111800^2 .

It is not a de Polignac number, because 18281473681 - 2⁹ = 18281473169 is a prime.

It is a super-2 number, since 2×18281473681² (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 (18281473381) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 67605 + ... + 202813.

Almost surely, 2^18281473681 is an apocalyptic number.

18281473681 is the 135209-th square number.

18281473681 is the 67605-th centered octagonal number.

It is an amenable number.

18281473681 is a deficient number, since it is larger than the sum of its proper divisors (135210).

18281473681 is an frugal number, since it uses more digits than its factorization.

18281473681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 270418 (or 135209 counting only the distinct ones).

The product of its digits is 516096, while the sum is 49.

Multiplying 18281473681 by its sum of digits (49), we get a square (895792210369 = 946463²).

The spelling of 18281473681 in words is "eighteen billion, two hundred eighty-one million, four hundred seventy-three thousand, six hundred eighty-one".