181398221 has 2 divisors, whose sum is σ = 181398222. Its totient is φ = 181398220.

The previous prime is 181398199. The next prime is 181398223. The reversal of 181398221 is 122893181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 100200100 + 81198121 = 10010^2 + 9011^2 .

It is a cyclic number.

It is not a de Polignac number, because 181398221 - 2⁶ = 181398157 is a prime.

It is a Sophie Germain prime.

Together with 181398223, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (181398223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90699110 + 90699111.

It is an arithmetic number, because the mean of its divisors is an integer number (90699111).

Almost surely, 2^181398221 is an apocalyptic number.

It is an amenable number.

181398221 is a deficient number, since it is larger than the sum of its proper divisors (1).

181398221 is an equidigital number, since it uses as much as digits as its factorization.

181398221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6912, while the sum is 35.

The square root of 181398221 is about 13468.4156826258. The cubic root of 181398221 is about 566.0798218031.

The spelling of 181398221 in words is "one hundred eighty-one million, three hundred ninety-eight thousand, two hundred twenty-one".