181681821 has 12 divisors (see below), whose sum is σ = 262668640. Its totient is φ = 121010760.

The previous prime is 181681811. The next prime is 181681847. The reversal of 181681821 is 128186181.

It is a happy number.

It is not a de Polignac number, because 181681821 - 2¹⁰ = 181680797 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 (181681811) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1920 + ... + 19158.

Almost surely, 2^181681821 is an apocalyptic number.

It is an amenable number.

181681821 is a deficient number, since it is larger than the sum of its proper divisors (80986819).

181681821 is a wasteful number, since it uses less digits than its factorization.

181681821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18416 (or 18413 counting only the distinct ones).

The product of its digits is 6144, while the sum is 36.

The square root of 181681821 is about 13478.9399063873. The cubic root of 181681821 is about 566.3746733654.

The spelling of 181681821 in words is "one hundred eighty-one million, six hundred eighty-one thousand, eight hundred twenty-one".