181605421 has 2 divisors, whose sum is σ = 181605422. Its totient is φ = 181605420.

The previous prime is 181605371. The next prime is 181605427. The reversal of 181605421 is 124506181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 124768900 + 56836521 = 11170^2 + 7539^2 .

It is a cyclic number.

It is not a de Polignac number, because 181605421 - 2²¹ = 179508269 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 181605421.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (181605427) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90802710 + 90802711.

It is an arithmetic number, because the mean of its divisors is an integer number (90802711).

Almost surely, 2^181605421 is an apocalyptic number.

It is an amenable number.

181605421 is a deficient number, since it is larger than the sum of its proper divisors (1).

181605421 is an equidigital number, since it uses as much as digits as its factorization.

181605421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1920, while the sum is 28.

The square root of 181605421 is about 13476.1055576157. The cubic root of 181605421 is about 566.2952724809.

The spelling of 181605421 in words is "one hundred eighty-one million, six hundred five thousand, four hundred twenty-one".