181901221 has 2 divisors, whose sum is σ = 181901222. Its totient is φ = 181901220.

The previous prime is 181901147. The next prime is 181901267. The reversal of 181901221 is 122109181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 126562500 + 55338721 = 11250^2 + 7439^2 .

It is a cyclic number.

It is not a de Polignac number, because 181901221 - 2⁹ = 181900709 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (181901281) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90950610 + 90950611.

It is an arithmetic number, because the mean of its divisors is an integer number (90950611).

Almost surely, 2^181901221 is an apocalyptic number.

It is an amenable number.

181901221 is a deficient number, since it is larger than the sum of its proper divisors (1).

181901221 is an equidigital number, since it uses as much as digits as its factorization.

181901221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 288, while the sum is 25.

The square root of 181901221 is about 13487.0760730412. The cubic root of 181901221 is about 566.6025674132.

The spelling of 181901221 in words is "one hundred eighty-one million, nine hundred one thousand, two hundred twenty-one".