81247517 has 4 divisors (see below), whose sum is σ = 87497340. Its totient is φ = 74997696.

The previous prime is 81247489. The next prime is 81247541. The reversal of 81247517 is 71574218.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 71574218 = 2 ⋅35787109.

It can be written as a sum of positive squares in 2 ways, for example, as 41229241 + 40018276 = 6421^2 + 6326^2 .

It is a cyclic number.

It is not a de Polignac number, because 81247517 - 2⁸ = 81247261 is a prime.

It is a super-3 number, since 3×81247517³ (a number of 25 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81247577) 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 in 3 ways as a sum of consecutive naturals, for example, 3124892 + ... + 3124917.

It is an arithmetic number, because the mean of its divisors is an integer number (21874335).

Almost surely, 2^81247517 is an apocalyptic number.

It is an amenable number.

81247517 is a deficient number, since it is larger than the sum of its proper divisors (6249823).

81247517 is a wasteful number, since it uses less digits than its factorization.

81247517 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6249822.

The product of its digits is 15680, while the sum is 35.

The square root of 81247517 is about 9013.7404555490. The cubic root of 81247517 is about 433.1151405810.

The spelling of 81247517 in words is "eighty-one million, two hundred forty-seven thousand, five hundred seventeen".