820908181 has 2 divisors, whose sum is σ = 820908182. Its totient is φ = 820908180.

The previous prime is 820908161. The next prime is 820908239. The reversal of 820908181 is 181809028.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 810313156 + 10595025 = 28466^2 + 3255^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-820908181 is a prime.

It is a super-2 number, since 2×820908181² = 1347780483265457522, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 820908181.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (820908161) 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, 410454090 + 410454091.

It is an arithmetic number, because the mean of its divisors is an integer number (410454091).

Almost surely, 2^820908181 is an apocalyptic number.

It is an amenable number.

820908181 is a deficient number, since it is larger than the sum of its proper divisors (1).

820908181 is an equidigital number, since it uses as much as digits as its factorization.

820908181 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9216, while the sum is 37.

The square root of 820908181 is about 28651.4952663905. The cubic root of 820908181 is about 936.3355829866.

The spelling of 820908181 in words is "eight hundred twenty million, nine hundred eight thousand, one hundred eighty-one".