81820069 has 2 divisors, whose sum is σ = 81820070. Its totient is φ = 81820068.

The previous prime is 81820033. The next prime is 81820073. The reversal of 81820069 is 96002818.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 48469444 + 33350625 = 6962^2 + 5775^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81820069 is a prime.

It is a super-2 number, since 2×81820069² = 13389047382329522, which contains 22 as substring.

It is equal to p_4769503 and since 81820069 and 4769503 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81820009) 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, 40910034 + 40910035.

It is an arithmetic number, because the mean of its divisors is an integer number (40910035).

Almost surely, 2^81820069 is an apocalyptic number.

It is an amenable number.

81820069 is a deficient number, since it is larger than the sum of its proper divisors (1).

81820069 is an equidigital number, since it uses as much as digits as its factorization.

81820069 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6912, while the sum is 34.

The square root of 81820069 is about 9045.4446546314. Note that the first 3 decimals coincide. The cubic root of 81820069 is about 434.1301488380.

The spelling of 81820069 in words is "eighty-one million, eight hundred twenty thousand, sixty-nine".