81205897 has 2 divisors, whose sum is σ = 81205898. Its totient is φ = 81205896.

The previous prime is 81205877. The next prime is 81205903. The reversal of 81205897 is 79850218.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 43309561 + 37896336 = 6581^2 + 6156^2 .

It is a cyclic number.

It is not a de Polignac number, because 81205897 - 2⁷ = 81205769 is a prime.

It is a Chen prime.

It is equal to p_4735849 and since 81205897 and 4735849 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (81205877) 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, 40602948 + 40602949.

It is an arithmetic number, because the mean of its divisors is an integer number (40602949).

Almost surely, 2^81205897 is an apocalyptic number.

It is an amenable number.

81205897 is a deficient number, since it is larger than the sum of its proper divisors (1).

81205897 is an equidigital number, since it uses as much as digits as its factorization.

81205897 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 40320, while the sum is 40.

The square root of 81205897 is about 9011.4314623150. The cubic root of 81205897 is about 433.0411718340.

The spelling of 81205897 in words is "eighty-one million, two hundred five thousand, eight hundred ninety-seven".