181220509 has 2 divisors, whose sum is σ = 181220510. Its totient is φ = 181220508.

The previous prime is 181220467. The next prime is 181220521. The reversal of 181220509 is 905022181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 102454884 + 78765625 = 10122^2 + 8875^2 .

It is a cyclic number.

It is not a de Polignac number, because 181220509 - 2¹¹ = 181218461 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 (181220539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90610254 + 90610255.

It is an arithmetic number, because the mean of its divisors is an integer number (90610255).

Almost surely, 2^181220509 is an apocalyptic number.

It is an amenable number.

181220509 is a deficient number, since it is larger than the sum of its proper divisors (1).

181220509 is an equidigital number, since it uses as much as digits as its factorization.

181220509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1440, while the sum is 28.

The square root of 181220509 is about 13461.8167050365. The cubic root of 181220509 is about 565.8949025937.

The spelling of 181220509 in words is "one hundred eighty-one million, two hundred twenty thousand, five hundred nine".