81636517 has 2 divisors, whose sum is σ = 81636518. Its totient is φ = 81636516.

The previous prime is 81636497. The next prime is 81636563. The reversal of 81636517 is 71563618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 49928356 + 31708161 = 7066^2 + 5631^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81636517 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81636587) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40818258 + 40818259.

It is an arithmetic number, because the mean of its divisors is an integer number (40818259).

Almost surely, 2^81636517 is an apocalyptic number.

It is an amenable number.

81636517 is a deficient number, since it is larger than the sum of its proper divisors (1).

81636517 is an equidigital number, since it uses as much as digits as its factorization.

81636517 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 30240, while the sum is 37.

The square root of 81636517 is about 9035.2928563495. The cubic root of 81636517 is about 433.8052688088.

The spelling of 81636517 in words is "eighty-one million, six hundred thirty-six thousand, five hundred seventeen".