181838363821 has 4 divisors (see below), whose sum is σ = 181843040700. Its totient is φ = 181833686944.

The previous prime is 181838363809. The next prime is 181838363869. The reversal of 181838363821 is 128363838181.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 128363838181 = 26141 ⋅4910441.

It can be written as a sum of positive squares in 2 ways, for example, as 101458175625 + 80380188196 = 318525^2 + 283514^2 .

It is a cyclic number.

It is not a de Polignac number, because 181838363821 - 2²¹ = 181836266669 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (181838333821) 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, 2279626 + ... + 2358043.

It is an arithmetic number, because the mean of its divisors is an integer number (45460760175).

Almost surely, 2^181838363821 is an apocalyptic number.

It is an amenable number.

181838363821 is a deficient number, since it is larger than the sum of its proper divisors (4676879).

181838363821 is an equidigital number, since it uses as much as digits as its factorization.

181838363821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4676878.

The product of its digits is 1327104, while the sum is 52.

The spelling of 181838363821 in words is "one hundred eighty-one billion, eight hundred thirty-eight million, three hundred sixty-three thousand, eight hundred twenty-one".