181371821 has 2 divisors, whose sum is σ = 181371822. Its totient is φ = 181371820.

The previous prime is 181371811. The next prime is 181371863. The reversal of 181371821 is 128173181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 106894921 + 74476900 = 10339^2 + 8630^2 .

It is a cyclic number.

It is not a de Polignac number, because 181371821 - 2¹⁰ = 181370797 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (181371811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90685910 + 90685911.

It is an arithmetic number, because the mean of its divisors is an integer number (90685911).

Almost surely, 2^181371821 is an apocalyptic number.

It is an amenable number.

181371821 is a deficient number, since it is larger than the sum of its proper divisors (1).

181371821 is an equidigital number, since it uses as much as digits as its factorization.

181371821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2688, while the sum is 32.

The square root of 181371821 is about 13467.4355762335. The cubic root of 181371821 is about 566.0523587768.

The spelling of 181371821 in words is "one hundred eighty-one million, three hundred seventy-one thousand, eight hundred twenty-one".