81135517 has 2 divisors, whose sum is σ = 81135518. Its totient is φ = 81135516.

The previous prime is 81135497. The next prime is 81135557. The reversal of 81135517 is 71553118.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 80030916 + 1104601 = 8946^2 + 1051^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81135517 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81135557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40567758 + 40567759.

It is an arithmetic number, because the mean of its divisors is an integer number (40567759).

Almost surely, 2^81135517 is an apocalyptic number.

It is an amenable number.

81135517 is a deficient number, since it is larger than the sum of its proper divisors (1).

81135517 is an equidigital number, since it uses as much as digits as its factorization.

81135517 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4200, while the sum is 31.

The square root of 81135517 is about 9007.5255758727. The cubic root of 81135517 is about 432.9160321261.

The spelling of 81135517 in words is "eighty-one million, one hundred thirty-five thousand, five hundred seventeen".