81785071 has 2 divisors, whose sum is σ = 81785072. Its totient is φ = 81785070.

The previous prime is 81785069. The next prime is 81785111. The reversal of 81785071 is 17058718.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81785071 - 2¹ = 81785069 is a prime.

Together with 81785069, it forms a pair of twin primes.

It is equal to p_4767607 and since 81785071 and 4767607 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81785071.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81785021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40892535 + 40892536.

It is an arithmetic number, because the mean of its divisors is an integer number (40892536).

Almost surely, 2^81785071 is an apocalyptic number.

81785071 is a deficient number, since it is larger than the sum of its proper divisors (1).

81785071 is an equidigital number, since it uses as much as digits as its factorization.

81785071 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15680, while the sum is 37.

The square root of 81785071 is about 9043.5098827833. The cubic root of 81785071 is about 434.0682412319.

The spelling of 81785071 in words is "eighty-one million, seven hundred eighty-five thousand, seventy-one".