81755717 has 2 divisors, whose sum is σ = 81755718. Its totient is φ = 81755716.

The previous prime is 81755671. The next prime is 81755743. The reversal of 81755717 is 71755718.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 80389156 + 1366561 = 8966^2 + 1169^2 .

It is a cyclic number.

It is not a de Polignac number, because 81755717 - 2²⁰ = 80707141 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81755797) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40877858 + 40877859.

It is an arithmetic number, because the mean of its divisors is an integer number (40877859).

Almost surely, 2^81755717 is an apocalyptic number.

It is an amenable number.

81755717 is a deficient number, since it is larger than the sum of its proper divisors (1).

81755717 is an equidigital number, since it uses as much as digits as its factorization.

81755717 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 68600, while the sum is 41.

The square root of 81755717 is about 9041.8868053078. The cubic root of 81755717 is about 434.0163036199.

Subtracting from 81755717 its reverse (71755718), we obtain a palindrome (9999999).

The spelling of 81755717 in words is "eighty-one million, seven hundred fifty-five thousand, seven hundred seventeen".