81565117 has 2 divisors, whose sum is σ = 81565118. Its totient is φ = 81565116.

The previous prime is 81565103. The next prime is 81565129. The reversal of 81565117 is 71156518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 69655716 + 11909401 = 8346^2 + 3451^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81565117 is a prime.

It is a super-2 number, since 2×81565117² = 13305736622447378, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81565147) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40782558 + 40782559.

It is an arithmetic number, because the mean of its divisors is an integer number (40782559).

Almost surely, 2^81565117 is an apocalyptic number.

It is an amenable number.

81565117 is a deficient number, since it is larger than the sum of its proper divisors (1).

81565117 is an equidigital number, since it uses as much as digits as its factorization.

81565117 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8400, while the sum is 34.

The square root of 81565117 is about 9031.3408196126. The cubic root of 81565117 is about 433.6787619804.

It can be divided in two parts, 8156511 and 7, that added together give a palindrome (8156518).

The spelling of 81565117 in words is "eighty-one million, five hundred sixty-five thousand, one hundred seventeen".